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Overview

This research paper examines the main procedural rules and principles applied to scientific and other expert evidence in criminal trials, taking criminal adjudication in England and Wales as its primary illustration. English criminal trials are “adversarial” and, in serious cases, tried before lay juries, but these distinctive institutional design features do not determine the shape and content of criminal procedure rules to the extent commonly assumed. By considering a fuller taxonomy of criminal procedure law we can see that many types of procedural rules – such as those regulating the flow of information to the fact-finder and helping to structure inferential reasoning, as well as rules promoting normative conceptions of procedural integrity and due process – are common, in some form, to all modern legal systems. Turning to more detailed analysis of trial procedure in one particular legal jurisdiction, the admissibility and uses of expert evidence in England and Wales are governed, firstly, by general evidentiary principles applicable to all types of evidence, and secondly, by criminal procedure doctrines specifically tailored to receiving and evaluating expert witness testimony. Both strands of evidentiary doctrine are summarized in this research paper, before concluding with some brief observations on possible reform options.

Institutional Contexts Of Criminal Trial Procedure

Criminal trials are formal, public, carefully orchestrated, and closely regulated institutional events, quite unlike ordinary everyday forms of social interaction and distinct, even, from just about every other public occasion of major social, cultural, and political significance. If modern states can be said to “govern through crime” (Simon 2007), criminal adjudication might be viewed as a nodal point in the constitution and reaffirmation of political authority, when the administration of criminal justice is at its most visibly “spectacular” (cf. Levenson 2008). Yet criminal trials also perforce involve human participants, some of whom have specialist training as judges and lawyers and cumulative experience as “repeat players” in criminal litigation; others, including most complainants and witnesses and many accused, have neither. Seasoned practitioners and uninitiated laypeople alike, however, share broadly similar biologically endowed cognitive capacities and limitations. One pervasive challenge in the design and operation of criminal trial proceedings, then, is to accommodate these extraordinary public events to the prosaic realities of human cognition, reason, and motivation.

Every system of criminal adjudication confronts this challenge more or less self-consciously and answers it – to the extent that it does – in its own distinctive way. There is no such thing as “free” forensic proof in any literal sense. The question is always how, and to what extent, a particular legal system seeks to manage and regulate the ways in which relevant information (“evidence”) is gathered, organized, presented, tested, and finally evaluated by the fact-finder. Various institutional tools, procedures, and mechanisms have been devised and adapted to this end. This research paper focuses specifically on the law of criminal trial procedure as one prominent regulatory technique. Legal cultures differ markedly even in their basic concepts and terminology. Common lawyers might be slightly puzzled by the notion of the “law of criminal trial procedure,” because they would generally refer to these trial rules as the law of criminal evidence and procedure, or simply as “the law of evidence.” But the Law of Evidence, as an identifiable legal specialism, is alien to civilian jurisprudence, which normally treats criminal procedure and civil procedure as separate branches of procedural law. My improvised terminology is intended to cover all of the rules of procedure and evidence which regulate criminal trials, both in Anglophone common law and in continental civilian legal jurisdictions.

It is sometimes thought that trial rules of evidence emerged in response to the adoption in England and, later, in the USA, of trial by jury, but this is misconceived (Schauer 2006). The functional separation between the common law judge, as master of the law, and lay juries as triers of fact makes it easier, in practice, to withhold information deemed unsuitable from the fact-finder than it would be in trial systems where the tribunal (whether a single judge, panel of judges, or mixed panel of judges and jurors) determines both law and fact. In criminal trials in England and Wales or the USA inadmissible evidence can be excluded from the trial without the jury’s ever knowing anything about it. But this functional convenience is not the reason for evidentiary exclusion. Evidence may be regarded as problematic quite irrespective of its validity or reliability – for example, because the way in which it was obtained or presented is regarded as being inconsistent with the normative requirements of a fair trial. Likewise, evidence obtained by torture is categorically inadmissible under Article 6 of the ECHR (Ga€fgen v Germany (2011) 52 EHRR 1), irrespective of whether the fact-finder is a professional judge or a lay jury (or an institutional hybrid). So while it is right to say that certain kinds of exclusionary rule – chiefly, those predicated on assumptions about lay jurors’ cognitive shortcomings – are characteristic of the common law world, rules of evidence and procedure, considered generically as tools for regulating criminal trials, are a universal feature of modern legal systems. There are important differences of degree and kind, but these distinctions can be drawn just as sharply within (cf. Roberts and Hunter 2012), as much as between, the idealized “adversarial” and “inquisitorial” procedural families.

Trials must always be viewed in procedural and temporal context. They are shaped to some extent by what comes after, and more particularly by what went before. Where juries give unreasoned general verdicts simply stating “guilty” or “not guilty,” as they generally do in serious criminal cases in common law jurisdictions, opportunities for post-verdict review may be severely curtailed. Criminal appeals against conviction in England and Wales can succeed only if the accused identifies some serious procedural defect in the course of his trial. In the absence of genuinely new evidence or arguments, claims of “actual innocence” will be met with the stony-faced response that the jury has already considered, and rejected, the accused’s protestations of innocence. The Court of Appeal is not empowered to substitute its own ex post evaluation of the evidence for the jury’s verdict. In this procedural environment, where opportunities for reviewing the quality of the jury’s output are limited, “input control” regulating the flow of information to the jury during the trial is at a premium. This plausibly accounts, in part, for the breadth, detail, and fastidiousness of evidentiary regulation that has evolved in common law jurisdictions (see Roberts and Zuckerman 2010), compared with the more freewheeling approach to receiving and evaluating evidence in Continental jurisdictions, where pretrial evidence gathering is routinely subject to much closer judicial supervision than it is in party-dominated adversarial systems and appeals against trial verdicts on points of law or fact are more freely available.

It is tempting to equate the law of evidence with exclusionary rules, and doing so tends to reinforce the widespread perception that detailed evidentiary regulation is a peculiarly common law preoccupation, while continental courts and jurists embrace “freedom of proof.” But this is fatuous, as Murphy (2010) rightly insists, because legal proof is never a no-holds-barred forensic scrum in which just anything goes. Irrespective of local technical exclusions, if any, there must be legally regulated and epistemically defensible standards, first, for assessing the relevance of potential evidence, and subsequently for determining its probative value, in the context of the case as a whole and in the light of the applicable burden and standard of proof. Forensic science and other expert evidence provides an excellent illustration of these general features of criminal adjudication. The fact-finder always needs to determine, among other things: what does expert evidence go to prove? Has it been adequately tested? Can it safely be relied on? Does it alone, or in combination with other evidence, satisfy the requisite standard of proof for finding the accused guilty of the offense or offenses charged?

Taxonomy Of Procedural Regulation Of Expert Evidence

Procedural rules, principles, and related normative standards can be classified in different ways. One might distinguish, for example, (i) rules constituting the court and delimiting its jurisdiction; (ii) rules for the conduct of trial proceedings; (iii) evidentiary rules of admissibility; (iv) forensic reasoning rules; and (v) rules for rendering judgment (see Roberts 2011: 395 ff.). Every modern criminal trial system has rules falling under each of these five subheadings, though of course their number and detailed specification vary enormously across individual legal systems. If we further subdivide part (iii) of the suggested taxonomy we might well discover that certain kinds of admissibility rule, for example, those directed towards preempting lay fact-finders from drawing impermissible inferences or falling prey to prejudicial reasoning, are particularly associated with common law jurisdictions and are found less frequently, or not at all, in the civilian legal world.

Regarding part (ii) of the taxonomy, common law trial systems generally adopt adversarial criminal trial procedures. Adversarial trials proceed as a kind of contest or debate between two partisan factions, each urging a different conclusion on the fact-finder, who must somehow reconstruct an accurate portrayal of disputed events from the evidential debris of full-blooded forensic conflict. Adversarialism pervades the broader institutional structures and cultural milieu of criminal adjudication in England and Wales. In a procedural system in which expert witnesses are instructed by adversarial parties, it is likely that experts will experience diffuse, and perhaps occasionally more concentrated, pressures to tailor their evidence to lawyers’ expectations (cf. Harris 2000). However, as independent advisors to the administration of justice whose advice is valued precisely because it is assumed to be scientifically valid and nonpartisan, there is only one type of advocacy that expert witnesses can afford to be drawn into, and that is advocacy promoting the integrity of their own, technical evidence.

Another significant trait of common law systems’ commitment to adversarial trial procedure is a reflex distrust of court-appointed experts. Although English judges notionally have a general common law power to instruct their own witnesses (R v Roberts (1985) 80 Cr App R 89, CA; R v Cleghorn [1967] 2 QB 584, CA), including experts (R v Holden (1838) 8 Car & P 606, 173 ER 638), this power is hardly ever exercised in criminal trials, and never to the exclusion of party-instructed expert witnesses. Depriving the accused of opportunities to develop the defense case by instructing scientific experts of his own choosing is presumptively unfair. Appearing to sanctify an expert’s testimony with the imprimatur of the court might also be regarded as detracting from judicial impartiality and trenching on the jury’s constitutional prerogatives. Yet without exclusivity, many of the vaunted advantages of courtappointed experts evaporate. For example, the fact-finder’s task is hardly made any easier by being confronted with a three-cornered scientific dispute involving court-appointed as well as party-instructed experts.

Mirjan Damasˇka (1986) has argued that countries with inquisitorial criminal procedures tend to be characterized by relatively high levels of social trust in state bureaucracies and professional expertise, whereas adversarial cultures are generally more suspicious of state officials and tend to place greater store by lay involvement in public decision-making, even if this sometimes entails contradicting expert opinion. Though admittedly drawn in sweeping and somewhat indistinct brush-strokes, Damasˇka’s suggestive parallels between a society’s political culture and its design preferences for legal procedure provide a more-than-plausible explanation of the markedly contrasting fortunes of courtappointed experts on different sides of the English Channel. Court experts flourish where officials dominate legal process and authoritative expert pronouncements are seldom challenged (a theoretical hypothesis confirmed in practice by the deference typically extended to expert evidence by Continental fact-finders: van Kampen and Nijboer 1997). Where, by contrast, the parties develop their own cases and dictate the course of legal proceedings, while professionals, experts, and officials of all kinds incite popular ambivalence and even a measure of suspicion, the court expert will not be held in comparably high esteem and is unlikely to be an acceptable surrogate for party-instructed expert witnesses.

The remainder of this research paper concentrates on parts (iii) and (iv) of my suggested taxonomy of criminal trial procedure rules. The next section on “General Principles of Admissibility” outlines general evidentiary doctrines applicable to all evidence, including scientific and other expert evidence. The following section then considers “Rules Specifically Regulating Expert Witness Testimony.” Descriptions of the logic of inferential fact-finding apply, more or less, to all modern systems of criminal adjudication because they relate to the cognitive capacities and limitations of human fact-finders. Other features of the analysis are indicative of broad trends within the common law world or apply to any jurisdiction in which criminal trial procedure is broadly speaking adversarial (a classification incorporating an expanding number of legal systems, partly owing to the influence of the ECHR). Ultimately, however, each legal jurisdiction has its own unique set of procedural rules, institutions, and processes, suffused with a distinctive legal culture. Precision can therefore be achieved only at the cost of parochialism. The relevant legal jurisdiction for my purposes is England and Wales, and I will cite English law examples by way of illustration. Scotland, Northern Ireland, and a host of other, smaller legal jurisdictions within the United Kingdom and the British Isles have their own independent criminal justice systems. Even within the UK’s legal jurisdictions there are major differences in criminal procedure, to say nothing of attempted comparisons with other common law systems of criminal adjudication in North America, Australasia, the Indian subcontinent, South East Asia, or the English-speaking parts of Africa. Generalizations about criminal adjudication in “common law” or “adversarial” systems may be useful signposts indicating likely assumptions and promising avenues for further inquiry, but they are always somewhat tendentious at the level of doctrinal detail or customary institutional practice.

General Principles Of Admissibility

General principles of admissibility apply to scientific evidence and expert witness testimony in addition to bespoke procedural rules. Scientifically impeccable expert evidence might therefore still be inadmissible at trial, if it infringes one or more of the general legal principles of admissibility discussed in this section pertaining to: (i) relevance, (ii) fair trial, (iii) hearsay, and (iv) character.

Relevance

Only relevant evidence is admissible in criminal trials. Evidence is worthless to the legal process unless it might help to resolve the (legally defined) issues in dispute. Relevant evidence might still be excluded on other grounds, but irrelevant information falls at the first hurdle: it is categorically inadmissible. “[T]o be relevant,” Lord Steyn observed in R v A (No 2) [2002] 1 AC 45, [31], “the evidence need merely have some tendency in logic and common sense to advance the proposition in issue.” While the weight or “probative value” of any piece of evidence may vary, depending on how persuasively or conclusively it proves (or disproves) a fact in issue, evidence is relevant if it has any probative value whatsoever, and irrelevant if it has none.

The low threshold of relevance mandated by English law is normally easily satisfied by forensic science or other expert evidence. A fingerprint or blood sample placing the accused at the scene of the crime is patently relevant; as are the results of drug tests, toxicological screens, questioned document analysis, pathology reports, and so on, whenever such information tends to confirm (or disprove) that a crime has been committed or to identify particular perpetrators. Indeed, such evidence is not merely relevant, but often of immense and sometimes decisive probative value. There are, however, two types of situations in which scientific evidence might fail to surmount the relevance hurdle to admissibility. The first is where scientific evidence relates to matters no longer in dispute in the litigation, as where the accused in a rape case admits the fact of intercourse, but claims that the complainant consented. In these circumstances, DNA evidence establishing that the accused was the donor of semen recovered from the complainant is no longer strictly relevant to any contested fact (though in practice the DNA report would still be adduced unopposed or submitted to the court as agreed evidence). A striking example is provided by Barry George’s successful appeal against his conviction of murdering the TV personality Jill Dando, partly on the basis of a single particle of firearms discharge residue (FDR) which was adduced at his trial to show that George had recently fired a gun. On appeal, it was conceded by forensic scientists that “the possibility that the FDR had come from the gun that killed Miss Dando was equally as remote as all other possibilities [including innocent contamination] and thus, on its own, entirely inconclusive”: R v George [2007] EWCA Crim 2722, [51]. In fact, evidence which is incapable of distinguishing between the prosecution’s case and the defense case, because it is equally likely under either hypothesis, would normally be regarded as irrelevant and should be excluded from the trial.

A second type of scenario conceivably raising relevancy objections concerns recent scientific discoveries or novel or idiosyncratic techniques. Since crack-pot theories, untested hypotheses, and unvalidated scientific techniques fail to satisfy even the threshold expectations of commonsense rationality, they are irrelevant in law, and consequently inadmissible in criminal trials. This is one basis on which, for example, the results of lie detector tests remain inadmissible in English (R v Chapman [2006] EWCA Crim 2545, [33]) and Scottish (HM Advocate v Sheridan [2011] HCJ 1) courts.

Fair Trial

Criminal justice cannot be achieved unless criminal proceedings, including trials, are conducted fairly. Dispensing justice demands due process of law, and justice must be seen to be done in order to sustain the moral legitimacy of criminal verdicts and foster their popular acceptability. Ensuring a fair trial has always been regarded as one of the judge’s most fundamental common law duties (R v Christie [1914] AC 545, HL), but this traditional precept has been reinforced and greatly expanded in recent decades by judicial innovation against a backdrop of the growing influence of human rights law (Roberts and Hunter 2012; Emmerson et al. 2007). Article 6 of the ECHR guarantees the right to a fair trial and elaborates a number of specific procedural rights for criminal suspects and the accused (Trechsel and Summers 2005). Crucially, the “right to a fair trial” is not limited to what takes place at trial. It also regulates criminal investigations (e.g., Teixeira de Castro v Portugal (1998) 28 EHRR 101), evidence gathering (e.g., Edwards and Lewis v UK (2005) 40 EHRR 24), and pretrial criminal procedure (e.g., Rowe and Davis v UK (2000) 30 EHRR 1).

Fair trial standards bear on the way in which evidentiary material is first obtained, its handling and storage, and defense access to scientific testing, results, and data in the pretrial process. Thus, irrespective of the scientific validity of a particular testing procedure, scientific results establishing – say – a suspected substance’s chemical composition or the identity of a perpetrator may still be ruled inadmissible at trial if the trace material on which the tests were conducted was obtained or retained illegally, if a proper chain of custody cannot be demonstrated to rule out the risk of accidental contamination (Pattenden 2008), or if test results were not disclosed to the defense when they should have been (ACPO/CPS 2010; R v Ward (1993) 96 Cr App R 1, CA). Proactive investigative methods can easily result in evidentiary exclusion if they are not carefully planned and monitored in order to keep criminal investigations within the bounds of propriety and preserve the integrity of their evidential product. Police “entrapment” is not a stand-alone defense in English criminal law (R v Sang [1980] AC 402, HL), but collusion by undercover officers or police informants which might be regarded as crossing the line into active incitement of criminality runs a serious risk that evidence of subsequent offending by a targeted suspect will be excluded (R v Looseley; Attorney General’s Reference (No.3 of 2000) [2001] UKHL 53, [2001] 1 WLR 2060). In particularly egregious circumstances, the trial judge may effectively throw the case out of court by staying proceedings indefinitely as an abuse of process (Choo 2008: Chap. 5).

The unifying normative thread linking police illegality, unfair investigative tactics, and failures of prosecution disclosure is procedural impropriety. Justice demands due process and fair trial. Irrespective of internal standards of scientific validity and methodological rigor, scientific or other expert evidence tainted by procedural impropriety is flawed, from a legal perspective, and it is consequently vulnerable to be being sacrificed – ruled inadmissible at trial – in order to preserve the procedural integrity of criminal adjudication.

Hearsay

In the adversarial common law tradition, the oral testimony of witnesses speaking live, on oath and in the presence of the jury in the courtroom is regarded as the paradigm of judicial evidence. The rule against hearsay is the alter ego of this principle of orality (Roberts and Zuckerman 2010: Chaps. 7 and 9). Witnesses must testify only to what they themselves have personally observed, heard, or otherwise perceived through their senses, and be available for cross-examination on the veracity and accuracy of their reported sensory perceptions. Mere hearsay – information told to the witness by somebody else, other people’s conversations overheard by the witness, and even the witness’s own out-of-court statements – does not qualify as original evidence in English criminal trials.

The hearsay prohibition could, in theory, be a major irritant for forensic science evidence. A great deal of the informational content of expert witness testimony is technically hearsay. Scientific literature and experimental data are compiled over many decades, or even centuries, by countless scientific researchers scattered across the globe. Any individual scientist can, at best, claim first-hand, personal knowledge of only a tiny fraction of the theoretical underpinnings and empirical substance of their courtroom testimony. Likewise, the generation of scientific evidence in individual cases is typically a collaborative enterprise. Trace evidence is routinely collected by scenes of crime officers (SOCOs) or Crime Scene Investigators (CSIs) and submitted to the forensic laboratory where one scientist might undertake preliminary screening, subsequently distributing evidential material to a lab technician who prepares samples, for a third colleague to undertake scientific testing, ultimately reporting to a fourth, more senior forensic scientist who interprets the test results in a final written report and will later testify to its contents in court if called upon to do so. Strictly speaking, however, most of this report is hearsay, because the testifying expert did not personally collect the samples, conduct the scientific testing, or record the data produced in court. With the exception of direct observations or interpretations for which the scientist can personally vouch, courtroom testimony repeats only what the scientist has been told by his or her colleagues, and this is classically hearsay. The same objection theoretically applies to forensic databases of fingerprints, shoeprints, tool-marks, firearms, glass composition, DNA profiles, and so forth, which are likewise compiled over extended periods of time, possibly in multiple locations, by scores or hundreds of individuals who may not even be identifiable at a later date, but at any rate will not be in court to testify to the continuity and reliability of the processes for collecting, testing, and retaining relevant samples on the basis of their own first-hand, personal knowledge.

In practice, courts in England and Wales have on pragmatic grounds largely exempted expert evidence from the operation of the hearsay prohibition. Information derived from general scientific literature, reference works, experimental data, and the common store of scientific knowledge is admissible in court provided that it is incorporated into, or subsumed within, the “opinion” of an appropriately qualified expert witness (R v Harris [2006] 1 Cr App R 5; CJA 2003, s.118(1) rules 1 and 8). Evidence of “matches” between crime scene trace evidence and samples or data contained on large-scale criminal justice databases are also admissible (R v Abadom [1983] 1 WLR 126, CA; R v Kempster (No.2) [2008] 2 Cr App R 19, CA). It might be thought that any other conclusion would be idiotic, in view of the tried-and-tested probative value of statistical and experimental data. However, the hearsay rule is a doctrine of conceptual logic rather than common sense, and it sometimes leads to counter-intuitive results, including, in the past, the exclusion of apparently reliable database evidence which cannot be “laundered” through expert testimony (Myers v DPP [1965] AC 1001, HL). The position is notably far less flexible in the USA, where suspects enjoy a constitutional right of confrontation in addition to being able to object to prosecution evidence on traditional hearsay grounds. In Melendez-Diaz v Massachusetts, 129 S Ct 2527 (2009), the US Supreme Court ruled, by a 5–4 majority, that drug analysts must be available to testify in person and undergo cross-examination, even though drug testing is mostly routine and uncontroversial and its results could easily be summarized in a short written report. Considerations of cost and convenience had to give way to the Sixth Amendment right to confrontation, as the Justices comprising the majority interpreted it.

Notwithstanding English courts’ evidentiary concessions, expert witnesses must still be cautious about their use of second-hand information relating to the current proceedings when writing their reports and testifying in court. For example, case details divulged to a forensic scientist by an investigating police officer, or factual information provided to the doctor who examines an injured complainant, or to a psychiatrist while interviewing the accused (e.g., R v Miah [2011] EWCA Crim 945, [60]; R v Hurst [1995] 1 Cr App R 82, CA) are all hearsay, and their legal status should be clearly flagged if experts make any reference to such alleged facts in their reports or testimony. Where an expert’s conclusions are built upon particular factual assumptions, the expert’s evidence is not even admissible, let alone persuasive, until the party calling the expert has laid an appropriate evidential foundation by proving the assumed facts through admissible, nonhearsay, evidence (Roberts 1996). If after the expert has already testified it turns out that the underlying facts cannot be established after all, the jury will be instructed to disregard the expert’s evidence in its entirety. Scientific evidence which, although internally valid, has no demonstrable factual connection to the matters disputed in the trial is legally irrelevant, and therefore inadmissible.

Character Evidence

A criminal trial in the common law world is an investigation into particularized allegations of wrongdoing, not a wide-ranging evaluation of the accused’s whole life and moral character. To the extent that character may be probative of conduct, however, there is room for admitting general character evidence at trial as material proof of the instant charge(s). This inferential logic applies to witnesses and complainants, whose character might be thought to shed light both on the events currently in dispute and on individuals’ testimonial credibility as witnesses in court. It also applies to the accused, who might, for example, have committed similar offenses in the past or revealed distinctive criminal tendencies or patterns or techniques of offending (a signature “m.o.,” modus operandi) through his previous – charged or uncharged – conduct.

Routine reliance by the prosecution on evidence of the accused’s previous convictions or other extraneous misconduct has generally been regarded as unfairly prejudicial in common law jurisdictions. Such evidence is not normally admissible unless its probative value is compelling (DPP v Boardman [1975] AC 421, HL; Makin v A.G. for New South Wales [1894] AC 57, PC). The Criminal Justice Act 2003 relaxed English law’s traditional aversion to character-based proofs, but evidence of the accused’s extraneous misconduct still remains subject to a special evidentiary regime requiring more than bare relevance to secure its admissibility at trial. The general common law prohibition on evidence of the accused’s bad character, and in particular on reasoning directly from propensity, still retains its traditional vitality in many parts of the English-speaking legal world.

It is conceivable that scientific evidence might be employed to link the accused to uncharged – or even previously acquitted (R v Z (Prior Acquittal) [2000] 2 AC 483, HL) – crimes in order to demonstrate the accused’s propensity for committing the type of offense currently before the court, in which case the evidence must satisfy the additional admissibility criteria specified by ss.101–106 of the Criminal Justice Act 2003. If the evidence is excluded, this will not reflect any inherent scientific defect, but rather the court’s judgment that revelations of extraneous misconduct would be unfairly prejudicial and disproportionate to the probative value of the evidence.

Fingerprint evidence and DNA matches potentially engage the law of bad character in more subtle ways. If it emerges during the course of a trial that the accused was first identified from a fingerprint left at another crime scene, or by a DNA profile derived from the National DNA Database (NDNAD), a savvy juror could easily infer that the accused must already have been “known to the police.” The NDNAD currently contains profiles not only from offenders, but also from suspects who were ultimately acquitted or not even charged in the first place. Jurors might therefore wrongly infer from a matching profile that the accused has a criminal record when, in fact, he has none. In (somewhat tardy) response to the judgment of the European Court of Human Rights in S and Marper v UK (2009) 48 EHRR 50, English law is currently being amended so that only the DNA profiles and fingerprints of convicted offenders will be retained on the NDNAD (Protection of Freedoms Act 2012). Even if this will in future preclude criminal juries from mistakenly inferring that the accused has a criminal record because his profile was on the NDNAD, trial judges should still strive to avoid, or failing that seek to neutralise, any unfair prejudice that could arise from gratuitous disclosures of the accused’s extraneous misconduct.

Character can be good as well as bad. Just as the prosecution may attempt to show that the accused has a propensity for engaging in distinctive types of criminality, the defense might try to invoke the accused’s character and previous conduct in order to persuade the fact-finder that the accused is “not the sort of person” who would do what he is alleged to have done. Although the accused enjoys an antique dispensation to adduce evidence of good reputation (R v Rowton (1865) 34 LJMC 57; 10 Cox CC 25, CCR), however, the law has traditionally frowned on self-serving evidence of disposition (R v Redgrave (1982) 74 Cr App R 10, CA), which is normally regarded as easily manufactured and probatively trifling. Accordingly, the general rule is that a party is prohibited from leading self-serving character evidence to “bolster the credit” of the party’s own witness. This prohibition operates, for example, to prevent a psychiatrist or psychologist who has examined the accused from advising the court that the accused is not a person disposed to violence, or that the accused is a truthful witness (R v Robinson (1994) 98 Cr App R 370, CA). Whether or not the accused was violent on the occasion in question, and whether his courtroom testimony should now be believed, are matters on which the jury is supposed to arrive at its own, common sense, judgments. It would be different if the accused or another witness was suffering from a clinical condition making him a pathological liar: the jury can always be informed of such expert medical or psychological diagnoses (Toohey v Metropolitan Police Commissioner [1965] AC 595, HL). In more recent pronouncements, the Court of Appeal has indicated somewhat “greater willingness to accept medical expert evidence on the issue of the credibility of a witness,” in accordance with its professed general inclination to be “more generous towards the admission of expert evidence than was once the case” (R v Pinfold and MacKenney [2004] 2 Cr App R 32, [14]– [15]; see Roberts (2004) for discussion).

Rules Specifically Regulating Expert Witness Testimony

We have established that admissible expert evidence must be relevant to the matters in dispute, consistent with procedural due process and the right to a fair trial, and compatible with complex legal doctrines governing hearsay and character evidence. In addition, to secure its admissibility expert evidence must also be (i) helpful to the jury; and (ii) presented by a competent, properly qualified expert. Finally, if it succeeds in being admitted, scientific and other expert evidence is subject to (iii) a clutch of evidentiary doctrines seeking to guide or constrain its uses in factfinding. These doctrines can be described, collectively, as “forensic reasoning rules” (Roberts and Zuckerman 2010: Chap. 15). They operate as instructions to the trial judge on how to direct the jury before jurors retire to deliberate on the evidence and produce a verdict. English criminal trial judges sum-up on the facts, as well as directing the jury on the applicable law; a practice not generally followed in US criminal trials. This gives the English trial judge a certain measure of practical influence over the jury’s evaluation of the evidence, though the judge must always stress that the jury has the final word on questions of fact. In any event, the jury deliberates in secret and will presumably only follow those judicial directions and suggestions which jurors both understand and, broadly speaking, endorse as sensible and appropriate.

Helpfulness: The Primary Criterion

There is no comprehensive statutory framework to regulate the admissibility of expert testimony in England and Wales. The applicable rules are almost entirely derived from judge-made case-law precedents. In the leading case of R v Turner [1975] 1 QB 834, 841–2, 843, CA, Lawton LJ explained that the trial judge had correctly excluded psychiatric evidence tendered by the defense, on the grounds that it would not have assisted the jury’s deliberations in this particular trial:

An expert’s opinion is admissible to furnish the court with scientific information which is likely to be outside the experience and knowledge of a judge or jury. If on the proven facts a judge or jury can form their own conclusions without help, then the opinion of an expert is unnecessary …. Jurors do not need psychiatrists to tell them how ordinary folk who are not suffering from any mental illness are likely to react to the stresses and strains of life …. [W]e are firmly of the opinion that psychiatry has not yet become a satisfactory substitute for the common sense of juries or magistrates on matters within their experience of life.

This passage has been taken as authority for the existence of a “common knowledge” rule, according to which expert evidence cannot be admitted if it concerns matters within the knowledge and experience of “ordinary folk” (Mackay and Colman 1991; Freckelton 1987: Chap. 3). Alternatively, or in addition, Turner is said to imply that expert evidence must be confined to mental abnormality as opposed to normal mental or psychological processes – an “abnormality rule” of admissibility (Sheldon and MacLeod 1991; Thornton 1995). More generally, Lawton LJ’s observations are held up as a typical example of legal ignorance and hostility towards science in general, and mental health professionals in particular. As later decisions have tended to confirm, however, Lawton LJ probably meant to insist on nothing more provocative than this banal proposition: expert evidence should be admitted in criminal trials only when, and just insofar as, it is likely to be genuinely helpful to the jury.

Turner’s critics rightly insist that expert testimony might still be helpful even if it concerns matters within jurors’ broad general knowledge or questions of normal human psychology. Jurors are unlikely to share an expert’s detailed, systematic knowledge of specific aspects of normal psychological processes, for example. Where “common sense” beliefs are a witches’ brew of genuine knowledge, mangled half-truths, urban myth, and popular invention, an expert might be able to help jurors disentangle fact from fiction so that they can evaluate the disputed evidence more objectively. It is for these sound reasons that English courts do not routinely insist on any “common knowledge” or “abnormality” criterion: such tests are rarely more than rough-and-ready rules of thumb to guide the application of the helpfulness standard in particular cases.

If English law really did propound a “common knowledge” rule, for example, expert evidence of identification from a photograph could not have been received in R v Stockwell (1993) 97 Cr App R 260, CA. Looking at photographs is hardly an arcane, specialist activity, yet the Court of Appeal endorsed the reception of expert evidence where it was felt that jurors would benefit from further assistance in a matter well within their everyday experience. Likewise, courts in England and Wales have received expert evidence of child psychology (e.g., DPP v A and BC Chewing Gum Ltd [1968] 1 QB 159, DC), without any suggestion that children, as a class, are “abnormal” or beyond the experience of ordinary people. Helpfulness, however, is a composite standard encompassing costs as well as benefits, and this is something Turner’s critics tend to overlook. Expert evidence may be misinterpreted or misunderstood, divert jurors’ attention into collateral issues, or waste time with cumulative proof of points already well-established by other evidence. Some forms of expert evidence may be especially prone to misinterpretation. It is widely held, for example, that lay jurors have a poor grasp of probability and statistical evidence, though there is disagreement about whether fact-finders are overawed by statistics or more commonly underestimate their true probative value (Koehler 2001; Lempert 1991; Tribe 1971). Irrespective of its theoretical relevance or weight, expert evidence is likely to be excluded if the trial judge is persuaded that it is probably going to be more trouble than it could be worth to hear it.

Helpfulness is the only master-key necessary to unlock the logic of admissibility decisions in England and Wales. Whether expert evidence will actually be admitted on any particular occasion turns on a detailed evaluation of all the available evidence in the case viewed in light of the parties’ respective litigation strategies, a factual matrix which will necessarily vary enormously from one trial to the next. Judicial assessments of the admissibility of expert evidence in the current proceedings may consequently be of limited value as legal precedents in subsequent cases.

Expert Qualification

English courts have demonstrated similar flexibility in their assessments of experts’ scientific credentials. The legal test of competence for expert witnesses adds little to the threshold relevancy standard, and operates in practice to promote the reception of expert testimony.

There is no requirement of formal training or paper qualifications, professional practice, or even membership of a relevant organization or learned society. The well-known case of R v Silverlock [1894] 2 QB 766, CCR, decided that a witness’s amateur interest and study were sufficient to qualify him as an expert in handwriting analysis. As Lord Russell of Killowen CJ explained, the question is simply whether or not the witness possesses expert knowledge relevant to an issue before the tribunal, irrespective of how he or she might have acquired it: “The question is, is he peritus? Is he skilled? Has he an adequate knowledge? …. There is no decision which requires that the evidence of a man who is skilled in comparing handwriting, and who has formed a reliable opinion from past experience, should be excluded because his experience had not been gained in the way of his business” (ibid. 771).

Case-law illustrations of English courts’ catholic conception of forensic “expertise” abound. A drug user with no scientific training or knowledge was permitted to identify a substance in his possession as cannabis (R v Chatwood [1980] 1 WLR 874, CA), while a police officer with experience in drug offenses could testify as an expert on the street price of heroin (R v Hodges [2003] 2 Cr App R 247, CA). It is perfectly proper for an artist to give “facial mapping” evidence, even though he has “no scientific qualifications, no specific training, no professional body and no database” (R v Stockwell (1993) 97 Cr App R 260, 264, CA; confirmed in R v Atkins [2010] 1 Cr App R 8, [2009] EWCA Crim 1876). In another memorable case, membership of the Inner Circle of Magic qualified a witness as “a highly expert magician” (Moore v Medley, The Times, 3 February 1955, cited by Smith (1995: 113)). Just about anybody who can provide the jury with specialist information relevant to the proceedings qualifies as an “expert” in English law.

Bespoke Forensic Reasoning Rules For Expert Evidence

Once questions of admissibility have been determined, the focus shifts to how evidence may be used in the trial. English criminal procedure law’s “forensic reasoning rules” come in various shapes and sizes. Some forensic reasoning rules are mandatory, notably including the trial judge’s obligation to direct the jury on the burden and standard of proof. Other doctrines prescribe flexible directions drawing the jury’s attention to the inherent infirmities of particular sorts of evidence, such as eye-witness identifications (R v Turnbull [1977] QB 224, CA) or the incriminating testimony of an erstwhile accomplice (R v Beck [1982] 1 WLR 461, CA) or warn the jury to resist slipping into enticing reasoning fallacies, such as misinterpreting the probative significance of a lie (R v Lucas [1981] QB 720, CA) and other forms of evidential “double-counting.”

A number of forensic reasoning rules pertaining specifically to expert evidence have been crafted by common law judges over the years. The most fundamental precept is that the jury is the ultimate arbiter of disputed facts, and must be clearly instructed to form its own view, even in relation to uncontradicted scientific, technical, or other expert evidence (e.g., R v Allen [2005] EWCA Crim 1344). As Lord President Cooper famously put it in Davie v Edinburgh Magistrates [1953] SC 34, 40, the role of the expert witness is “to furnish the judge or jury with the necessary scientific criteria for testing the accuracy of their conclusions, so as to enable the judge or jury to form their own independent judgment by the application of these criteria to the facts proved in evidence.” Legal commentators differ on the extent to which “juror education” is a practically feasible aspiration for legal adjudication (Allen 1994; Imwinkelreid 1997; Edmond 1998). It is implausible to imagine that a short, intensive course of juror education within the context of criminal trial proceedings could truly substitute for an expert’s long years of education, training, and practical experience. But jurors can at least be expected to exercise their critical faculties in deciding to rely on expert evidence bearing on contested factual issues. Measured, reflective, rational deference to expertise should not be equated with slavish acceptance or abdication of deliberative responsibility. And the jury must emphatically retain its sovereignty in determining “factual” questions with a normative dimension, such as whether the accused was “grossly negligent” (e.g., R v Misra and Srivastava [2005] 1 Cr App R 21, [2004] EWCA Crim 2375) or acted with diminished “mental responsibility” (e.g., R v Dietschmann [2003] 1 AC 1209, HL).

Rational deference to expertise might be an attractive option when the jury is presented with uncontradicted expert evidence, but how should the jury proceed in cases where experts called by the adversarial parties disagree? The answer is that the jury should do its common sense best to interpret the experts’ disagreement in the light of all the evidence in the case and its relevance to the charges and the facts in issue. Ultimately, in cases of enduring uncertainty or doubt, the criminal burden and standard of proof weigh in favor of an acquittal (e.g., R v Cannings [2004] 1 WLR 2607, CA). It is sometimes argued that cases involving disagreements between experts should attract a special judicial direction, but the Court of Appeal has resisted the notion that there is some ubiquitous form of words that must be used to cover this situation (R v Hookway and Noakes [2011] EWCA Crim 1989). The judge is merely required to do what trial judges must do in every case: to summarize fairly and fully any factual disagreement between the (expert) witnesses, indicate the potential salience of that disagreement for the questions that need to be determined, and leave the rest to the jury’s good sense.

It should already be apparent from the preceding discussion that a firm presupposition of lay jurors’ expertise in common sense reasoning is cemented into the institutional architecture of English criminal adjudication. Attempts to encourage the jury to depart from its ordinary reasoning processes are consequently frowned upon. Thus, in a case in which a defense expert encouraged jurors to apply Bayes’ Theorem to contested evidence, the Court of Appeal thundered:

[T]he attempt to determine guilt or innocence on the basis of a mathematical formula, applied to each separate piece of evidence, is simply inappropriate to the jury’s task. Jurors evaluate evidence and reach a conclusion not by means of a formula, mathematical or otherwise, but by the joint application of their individual common sense and knowledge of the world to the evidence before them. (R v Adams [1996] 2 Cr App R 467, 481)

Moreover, the “ultimate issue” of determining the accused’s guilt or innocence is always reserved to the fact-finder. The courts are assiduous in ensuring that “trial by expert,” or even “trial by science,” is never allowed to usurp the constitutional functions of trial by judge and jury. As Lawton LJ intoned in Turner, “We do not find that prospect attractive and the law does not at present provide for it” ([1975] 1 QB 834, 842).

The way in which juries are expected to reason about forensic science and other expert evidence has further implications for the way in which expert witnesses are expected to present their evidence in the courtroom. Expert testimony must be reasonably intelligible to lay people and communicated in a manner that successfully conveys its true probative significance. Thus, English courts have striven to ensure that DNA profiling evidence does not inadvertently encourage jurors (or trial judges directing them) to commit the well-known “prosecutor’s fallacy,” as reproduced by the Court of Appeal in R v Doheny and Adams [1997] 1 Cr App R 369, 372–373:

Only one person in a million will have a DNA profile which matches that of the crime stain.
The defendant has a DNA profile which matches the crime stain.
Ergo there is a million to one probability that the defendant left the crime stain and is guilty of the crime.

Deduction (3) is clearly fallacious, because “one in a million” is the frequency of the DNA profile in the suspect population, not the probability that the accused is the source of the profiled crime stain. If there were, say, four million people in the relevant suspect population, one would expect to find four individuals, plus the actual donor of the crime stain (who may or may not be the accused), with that matching DNA profile. Taking the profiling evidence in isolation, the probability that the accused is the source of the crime stain is actually 1-in-5 or 0.2. Glaring and pronounced though the fallacy seems when illustrated through simple hypotheticals, anecdotal evidence suggests that it may occur in practice with alarming regularity. English courts have attempted to insulate the jury from its distorting impact by insisting that a forensic scientist “should not be asked his opinion on the likelihood that it was the defendant who left the crime stain, nor when giving evidence should he use terminology which may lead the jury to believe that he is expressing such an opinion” (ibid. 374: generally, see Puch-Solis et al. 2012; Redmayne 2001).

More recently, in R v T [2011] 1 Cr App R 9, [2010] EWCA Crim 2439, the Court of Appeal went so far as to say that experts should not even employ likelihood ratios in their own case-work in the absence of a robust statistical basis to support further quantitative analysis. This was something of an overreaction (Redmayne et al. 2011), but the Court’s chief concern was entirely legitimate. It feared that the expert, who testified regarding footwear marks, was building factual assumptions into his evidence which were being concealed from the jury at trial. Experts’ own inferential reasoning needs to be transparent so that the jury can perform its designated role as fact-finder, rather than simply being presented with an expert witness’s inferential conclusions as a forensic fait accompli. These procedural rules are perhaps best categorized as supplementary admissibility standards, regulating not so much what information can be adduced at trial but how it may be presented. But their rationale is evidently rooted in traditional conceptions of the methodology and status of jury fact-finding in English criminal adjudication, and particularly when expressly incorporated into the trial judge’s summing-up to the jury, these procedural requirements are also aptly characterized as forensic reasoning rules.

Future Prospects: Reliability Through Reform?

Functional competence and “Turner helpfulness” constitute a flexible and relatively undemanding framework of bespoke admissibility standards, which in practice (and with the possible exception of certain kinds of behavioral science evidence) tends to militate in favor of receiving relevant expert witness testimony even when its probative value is sometimes questionable. Indeed, it might be said that English law has been rather too liberal in receiving scientific evidence in criminal trials, with too little scrutiny of its scientific credentials (Roberts 2008; Ormerod 2002). Some purported science is only “junk science” (Bernstein 1996; Huber 1991); not all forensic experts are properly qualified, and a few may be irresponsible charlatans. Even genuine experts might unwittingly propound false theories, make operational errors in their testing or calculations, or overstep the boundaries of their legitimate expertise. The question then arises as to whether criminal trial procedure is sufficiently well-insulated from fake science and bogus experts, and capable of distinguishing between valid and invalid scientific claims. Given that the whole system of criminal adjudication is predicated on lay fact-finders utilizing ordinary common sense techniques – principally listening to the testimony and observing the demeanor of witnesses who appear before them in the courtroom – ensuring scientific validity obviously poses a major design challenge for English criminal proceedings.

Promoting the validity and reliability of scientific and other expert evidence might be achieved in various ways. One might attempt to regulate forensic science providers directly, to subject crime labs to schemes of accreditation and performance management, or to compile registers of appropriately qualified experts certified courtsafe. One might rely on internal professional regulation and codes of professional ethics to maintain standards. There is a sense in which criminal litigation itself exerts a kind of market pressure on expert witnesses, since experts judged poor by the adversarial party hiring them are unlikely to be instructed again in future cases. (However, this is a very imperfect market by any standards, and may be warped by perverse incentives: the most effective courtroom performers, who delight their instructing lawyers time after time, might be poor scientists or willing to indulge in unethical behavior in order to help “their” side win the case.) It is likely that an effective legal framework for promoting and monitoring the quality of forensic science evidence and expert witness testimony would incorporate several, and perhaps all, of these complementary strategies. A final question to consider is whether reform of existing trial procedure law should form part of a comprehensive regulatory package in England and Wales (or anywhere else).

Drawing on the experiences of other common law jurisdictions, and in particular the “Daubert trilogy” in the USA (Berger 2011), the Law Commission (2011) has recently recommended the introduction in England and Wales of an enhanced judicial gatekeeping function in relation to expert evidence. The basic idea, modeled on Daubert v Merrell Dow 113 S Ct 2786 (1993), is that, whenever the reliability of expert evidence proffered by the prosecutor or defense lawyers is challenged, the trial judge ruling on admissibility should be obliged to undertake a preliminary assessment of its validity and reliability, by reference to an open-ended list of statutory criteria. The proposed statutory criteria include “generic factors” like data quality and completeness, appropriateness of methodology, soundness of inferential conclusions, and extent of peer review, and make provision for supplementary “factors for specific fields” to be added by the Lord Chancellor through delegated legislation.

It remains to be seen whether these recommendations will find their way onto the statutebook. US courts’ mixed experiences with Daubert over the last two decades (Risinger 2007) clearly demonstrate that investing trial judges with a gatekeeping duty to scrutinize the validity and reliability of scientific and other expert evidence does not, at a stroke, solve all the practical problems associated with expert witness testimony in the courtroom. It could, indeed, create new difficulties. In its preliminary consultation paper the Law Commission (2009: 1.13) wisely cautioned that “reforming the law governing the admissibility of expert evidence would not provide a panacea.” Re-engineering formal admissibility rules does not necessarily alter judicial culture or practice, or to the extent that it does, adaptive behavior may defeat reformers’ expectations. There is potentially greater scope for effective intervention in pretrial proceedings, for example, through comprehensive pretrial disclosure and judicial encouragement to agree scientific evidence and narrow down the issues for trial. These are now prime objectives of proactive judicial trial management in England and Wales, within the framework of the Criminal Procedure Rules first promulgated in 2005 (see, e.g., R v Reed and Reed [2010] 1 Cr App R 23; [2009] EWCA Crim 2698). None of this amounts to an argument against reforming rules of admissibility, if reform is desirable and well-executed. It simply reaffirms the truism that the law of criminal trial procedure is only one among many influences on the conduct and outcomes of criminal adjudication, not least in trials involving scientific evidence or expert witness testimony.

Bibliography:

ACPO/CPS (2010) Guidance booklet for experts: disclosure – experts’ evidence, case management and unused material. CPS Strategy and Policy Directorate, London. www.cps.gov.uk/publications/prosecution/ index.html. Accessed 14 Feb 2013
Allen RJ (1994) Expertise and the Daubert decision. J Crim Law Criminol 84:1157–1175
Berger MA (2011) The admissibility of expert testimony. In: Federal Judicial Center and National Research Council, Reference manual on scientific evidence, 3rd edn. National Academies Press, Washington, DC, pp 11–36
Bernstein DE (1996) Junk science in the United States and the Commonwealth. Yale J Int Law 21:123–182
Choo AL-T (2008) Abuse of process and judicial stays of criminal proceedings, 2nd edn. Oxford University Press, Oxford
Damasˇka MR (1986) The faces of justice and state authority: a comparative approach to the legal process. Yale University Press, New Haven
Edmond G (1998) The next step or moonwalking? Expert evidence, the public understanding of science and the case against Imwinkelried’s didactic trial procedures. Int J Evidence Proof 2:13–31
Emmerson B, Ashworth A, Macdonald A (2007) Human rights and criminal justice, 2nd edn. Sweet & Maxwell, London
Freckelton IR (1987) The trial of the expert. Oxford University Press, Melbourne
Harris GC (2000) Testimony for sale: the law and ethics of snitches and experts. Pepperdine Law Rev 28:1–74
Huber PW (1991) Galileo’s revenge: junk science in the courtroom. Basic Books, New York
Imwinkelreid EJ (1997) The next step in conceptualizing the presentation of expert evidence as education: the case for didactic trial procedures. Int J Evidence Proof 1:128–148
Koehler JL (2001) The psychology of numbers in the courtroom: how to make DNA-match statistics seem impressive or insufficient. South Calif Law Rev 74:1275–1305
Law Commission (2009) The admissibility of expert evidence in criminal proceedings in England and Wales. LCCP No 190, TSO, London
Law Commission (2011) Expert evidence in criminal proceedings in England and Wales. Law Com No 325, TSO, London
Lempert R (1991) Some caveats concerning DNA as criminal identification evidence: with thanks to the Reverend Bayes. Cardozo Law Rev 13:303–341
Levenson LL (2008) Courtroom demeanor: the theater of the courtroom. Minnesota Law Rev 92:573–633
Mackay RD, Colman AM (1991) Excluding expert evidence: a tale of ordinary folk and common experience. Criminal Law Rev 800–810
Murphy P (2010) No free lunch, no free proof: the indiscriminate admission of evidence is a serious flaw in international criminal trials. J Int Criminal Justice 8:539–573
Ormerod D (2002) Sounding out expert voice identification. Criminal Law Rev 771–790
Pattenden R (2008) Authenticating “things” in English law: principles for adducing tangible evidence in common law jury trials. Int J Evidence Proof 12:273–302
Puch-Solis R, Roberts P, Pope S, Aitken C (2012) Assessing the probative value of DNA evidence. Royal Statistical Society, London. www.rss.org.uk/ site/cms/contentviewarticle.asp?article¼1132
Redmayne M (2001) Expert evidence and criminal justice. Oxford University Press, Oxford
Redmayne M, Roberts P, Aitken C, Jackson G (2011) Forensic science evidence in question. Criminal Law Rev 347–356
Risinger DM (2007) Goodbye to all that, or a fool’s errand, by one of the fools: how i stopped worrying about court responses to handwriting identification (and “forensic science” in general) and learned to love misinterpretations of Kumho Tire v Carmichael. Tulsa Law Rev 43:447–475
Roberts A (2008) Drawing on expertise: legal decision- making and the reception of expert evidence. Criminal Law Rev 443–462
Roberts P (1996) Will you stand up in court? On the admissibility of psychiatric and psychological evidence. J Forensic Psychiat 7:61–76
Roberts P (2004) Towards the principled reception of expert evidence of witness credibility in criminal trials. Int J Evidence Proof 8:215–232
Roberts P (2011) Groundwork for a jurisprudence of criminal procedure. In: Duff RA, Green S (eds) Philosophical foundations of criminal law. Oxford University Press, Oxford, pp 379–408
Roberts P, Hunter J (eds) (2012) Criminal evidence and human rights: reimagining common law procedural traditions. Hart, Oxford
Roberts P, Zuckerman A (2010) Criminal evidence, 2nd edn. Oxford University Press, Oxford
Schauer F (2006) On the supposed jury-dependence of evidence law. Univ Pennsylvania Law Rev 155:165–202
Sheldon DH, MacLeod MD (1991) From normative to positive data: expert psychological evidence re-examined. Criminal Law Rev 811–820
Simon J (2007) Governing through crime: how the war on crime transformed American democracy and created a culture of fear. Oxford University Press, New York
Smith JC (1995) Criminal evidence. Sweet & Maxwell, London
Thornton P (1995) The admissibility of expert psychiatric and psychological evidence – judicial training. Med Sci Law 35:143–149
Trechsel S, Summers SJ (2005) Human rights in criminal proceedings. Oxford University Press, Oxford
Tribe LH (1971) Trial by mathematics: precision and ritual in the legal process. Harv Law Rev 84:1329–1393
van Kampen P, Nijboer H (1997) Daubert in the Lowlands. UC Davis Law Rev 30:951–995