Scientific Basis Of The Forensic Process Research Paper

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This research paper reviews the contributions to the History and Philosophy of Science (HPS) that impact on the scientific basis of the forensic process. There is a close parallel between the scientific method and the forensic process, in that each consists of hypothesis creation, testing and review based on observations and rigorous challenge. The leaders in HPS whose thoughts are most relevant are Popper, for his views on the limitations of inductive reasoning, Peirce, for introducing the concept of abduction, Kuhn for his view on “normal science” and the sociology of scientific developments, and Lakatos, for formalizing Popper’s views into what he termed research programs.

Having established the scientific foundation of the forensic process, the paper turns to how it is used to convert “science” into knowledge in the form of evidence arising from an investigation and of relevance to the determination of facts by a tribunal. The fundamental types of forensic evidence, classified by purpose, are described, leading to a taxonomy of forensic evidence based on the principles of rhetoric.

Is It Science?

There is no definition of “forensic science” that addresses the question of its scientific basis. Most definitions are constructed around the concepts of “science applied to the law” and “working carefully”, but these beg more questions than they answer. Is parentage testing for immigration purposes forensic? What about dope testing of Olympic athletes, or race horses? Is investigation of environmental spills forensic? Where does pre-employment drug screening fit? And “working carefully” encompasses pilots, accountants, and surgeons, but that clearly does not make them forensic.

Adopting the approach that it is something conducted by scientists in the laboratory does not help much either. For example, aspects of a homicide investigation that could be classed as “forensic” may be conducted at the scene by personnel as diverse as those who are serving police officers and whose qualification consists of successful completion of high school together with in-service training, and by toxicologists and DNA analysts with a Ph.D. degree working in a university or private laboratory.

Not too long ago, such questions would have seemed too academic and abstract for a work on forensic science, the forensic literature was dominated by case reports and papers describing new or improved technical methods. That should never have been so and is certainly less so today. The relatively recently published report by the National Academies of Science on forensic science in the US was highly critical of forensic science in general, and aspects of crime scene-related criminalistics such as tool marks and fingerprints in particular, for not being well-founded in science. The UK too has embraced basic scientific philosophy in evaluation of forensic evidence, where proposed legislation on the admissibility of expert evidence requires that a trial judge may refuse to admit expert evidence that is based on a hypothesis which has not been subjected to scrutiny (including experimental or other testing) or has failed to stand up to scrutiny.

However, the main unanswered question, other than a superficial passing mention in the NAS report, is what exactly is science?

This research paper addresses these issues by first of all exploring what science really is, then defining and exploring the forensic process, and thereby demonstrating how the forensic process is indeed fundamentally a scientific endeavor, with all the advantages and limitations that arise from that. The paper ends by addressing the question “does it matter whether or not it is based in science” and explores some consequences.

Science, Technology, And The Scientific Method

The word “science” is derived from the Latin verb scire, to know, and its noun scientia, knowledge. Although the principles of the scientific method can and have been applied to other areas including psychology and the social sciences, the accepted usage today is knowledge of the natural world. Hence the generally accepted perspective of forensic science as a source of unqualified and independent information, but the history of the scientific method and the writings of the philosophers of science tell us that science is not absolute.

The ancient Chinese and early Muslim societies contributed many discoveries and inventions relevant to natural laws, but “knowledge”, including scientific knowledge, in western societies is built on the foundations provided by the ancient Greeks and Romans. As a result, up until the early sixteenth century, philosophers formulated what they regarded as laws of nature based on the universal belief that the Earth was the center of the Universe. Thus it was “known” that the Earth was at rest in the centre of the universe. This was a natural and inevitable conclusion arising from the form of deductive logic that prevailed at the time, namely that having accepted certain propositions we can increase our knowledge by using those to predict outcomes, and so new propositions come into being.

This changed dramatically when Nicolaus Copernicus (1473–1543) decided to test the accepted knowledge by carrying out observations on the heavenly bodies to see if they behaved as predicted. They did not, and the scientific method was born.

The next century reinforced the importance of inductive logic in developing our knowledge of the natural world. Francis Bacon (1561–1626) described what is still today accepted as the essence of the scientific method, namely the cycle of observations to determine facts, followed by application of inductive reasoning to formulate a hypothesis that explains the observations, followed by further experimentation to test the hypothesis, resulting in its acceptance, refinement or rejection. Bacon’s ideas were central to the subsequent three centuries of scientific enlightenment, and stimulated interest in science as an area of study in its own right.

The core of Bacon’s scientific method is the role of the hypothesis. It is the link between observation and interpretation, and one that requires the utmost rigor in its application. Contrary to the popular expression, facts do not speak for themselves. The same observations can satisfy many interpretations, and many of the advances in what can be regarded as “scientific” are concerned with the relationship between observation, hypothesis, and interpretation. A fact is something known or proven to be true and may therefore be assumed to be the starting point or end point of the cycle, but “facts” themselves may indeed not be objective, proven, immutable entities, but may be subjective perceptions or interpretations of some consequence of a true fact.

The work of the American philosopher of science Charles Sanders Peirce (Peirce 1934) is central to the understanding of the strengths and weaknesses of the science that underpins forensic science, especially in regard to current controversies regarding contextual bias. Before Peirce, scientific enquiry was either inductive, that is, making inferences from a particular set of phenomena in order to predict and make propositions of more general character (empiricism), or deductive, that is, inferring from accepted truths and using general laws to deduce outcomes (rationalism). He introduced a third option, “abduction,” using the formulation and testing of hypotheses to explore possible explanations for a surprising event or occurrence, one in which there is no existing set of phenomena. Abduction therefore gives us an alternative entry point into the scientific method, and of course in this context criminal offences are almost always surprising events.

In practical terms the hypothesis is the scientist’s best guess of the character of phenomena that he or she is going to investigate. Intuitively, the validity or strength of any guess will be proportionate to the quality and extent of the information on which it is based. Abduction is therefore counter-intuitive but provides the most fertile although least secure mode of inference. The hypothesis, being based on a “surprise event” and lacking a foundation of pre-existing phenomena, needs to have practical implications that can be rigorously tested.

Peirce himself was aware of the limitations of abduction as well as its advantages. He expressed it thus: “Deduction proves that something must be; Induction shows that something actually is operative; Abduction merely suggests that something may be.”

A functional definition of forensic science is that it is concerned with identifying objects at a crime scene that can be used to provide a credible reconstruction of the event (Tilstone et al. 2012), and induction, abduction and deduction are all essential elements of the process in deriving that reconstruction. The surprise event is the crime itself and trying to explain what happened begins with the formulation of an explanatory hypothesis, followed by its testing and refinement. However, the information available as a consequence of that one event, the crime, is an insufficient basis for the conventional inductive approach to hypothesis formulation. On the other hand abduction is an imaginative, “what if,” process that enjoys exploring the unexpected, captures the intuitive actions of the crime scene investigator, and can lead to formulation of one or more credible hypothesis. Peirce established abduction as a legitimate element of the scientific method, but the imaginative beginning must be balanced by rigorous, objective, scrutiny of alternate hypotheses and testing of their validity.

How then can a hypothesis be evaluated with a view to establish whether it is a matter of fact and not just a possible explanation? The cycle of the scientific method demonstrates that science is not an absolute, but a continuous process of searching for the truth, and therefore cannot prove any hypothesis to the exclusion of everything else. Karl Popper (Popper 1970) was a key figure in the debate. He held that all observation is from a point of view, and therefore any conclusion drawn from observations will be colored consciously or sub-consciously by our existing understanding. This by the way was 40–50 years before the “discovery” of contextual bias in the forensic sciences.

Popper’s critical rationalism challenged the prevailing thinking in science, which held that a theory could be verified and thus acknowledged as being true on the basis of direct observations in the natural world. At its simplest, Popper’s view is that no amount of confirmation proves a theory but one reliable falsification disproves it.

This point was controversial in that the prevailing theory of science preceding Popper was one that relied on empirical observation as the basis of drawing scientific conclusions. If one could make direct observations in the world which supported one’s theory – then the theory was believed to be verified and thus could be acknowledged as true.

Popper used a simple example to illustrate his disagreement. Everyone in Europe and North America knew that all swans were white, but the exploration of Australasia was accompanied by the discovery of black swans, thereby challenging the accepted situation and leading to refinement of the properties that define “swan.” Using this and other examples, Popper successfully argued that using observation to verify a theory does not necessarily result in secure knowledge or empirical truth. He proposed that seeking to falsify theories rather than verify them was a much more reliable way in which to produce knowledge that could be trusted.

Falsification is a simple and powerful tool for testing scientific hypotheses. Sadly it is one that seems to have been beyond the wit of the then US Supreme Court Chief Justice, at the time of the Court’s decision in Daubert –vMerrel Dow. It is itself not absolute, however, and apparent falsifications have to be subject to the same scrutiny as any other element of a hypothesis. Observations may produce information that apparently falsifies a hypothesis, but further testing may provide an explanation that maintains the integrity of the law. Such was the case with the discovery of the planet Neptune. The development of better telescopes led to the observation that the orbit of the planet Uranus was not as predicted by Newton’s laws. Rather than reject Newton’s laws which had stood the test of time, astronomers searched for an explanation, the most likely of which was the presence of a hitherto undiscovered planet. And so it turned out when Neptune was observed in 1846, in exactly the predicted place.

These examples – the black swans and the discovery of Neptune – show that an essential element of a good theory is its ability to predict something or even better forbid it, and this is as true for the specific application of science in forensic investigations as it is for science in general.

Mention was made above of how Popper’s falsification challenged the status quo of the scientific method at the time. This leads to an alternate approach to defining science, by focusing on the behaviors of scientists rather than seeking an explanation of “science” based on the methods used or framework within which they work.

This was the approach taken by Thomas Kuhn (Kuhn 1966) who argued that scientists work within a conceptual paradigm that strongly influences the way in which they see data. Kuhn was interested in the way that science advances, and differentiated between what he called normal science, which progresses incrementally, little by little, and revolutionary science, where no change occurs until there is overwhelming evidence to overcome the prevailing paradigm which is then cast aside and replaced by the new.

In conducting his research Kuhn had to grapple with the essential question of what “science” is in order to be able to discuss how changes come about in scientific theories. He concluded that it is defined by communities of practitioners sharing properties related to the manner in which they conduct the exploration of knowledge about some aspect of the physical world. It is the existence of these communities and their established norms that make the paradigm such a strong force, inevitably resulting in conservatism.

Imre Lakatos is the last of the scientific philosophers to be considered here, but by no means the least, certainly in considering the foundation principles of forensic science. Lakatos was concerned that a strict and unthinking interpretation of Popper’s falsification concept meant a hypothesis would be rejected, but its core usefulness might still be valid but lost (Lakatos 1970). Any apparent falsification should not be accepted without question, but may instead point the way to further refinement and improvement of the apparently false hypothesis.

To remedy what he saw as a problem with Popper’s theory Lakatos introduced the concept of “research programmes” as a solution. A research programme is the aggregate of several theories which share a core and that progress using a common set of methodologies. In Lakatos’ approach, a scientist works within a “research program” that corresponds roughly with Kuhn’s “paradigm.” Whereas Popper rejected the use of ad hoc hypotheses as unscientific, Lakatos accepted their place in the development of new theories, as of course did Peirce.

The main contribution to forensic science made by Lakatos is his insistence on incorporating the concept of ceteris paribus into the evaluation of a hypothesis. Translated as “other things being equal,” ceteris paribus provides a context in which the formulation of a hypothesis and its acceptance, rejection, or modification depend on the state of our knowledge at the time. Its significance can be summarized as “We don’t know what we don’t know” and future discoveries – either new and unsuspected information like black swans or apparent contradictions to a well-established theory like Newton’s law – can alter the interpretation of observations.

In summary, a single exact definition of science has eluded philosophers of science, but whether it is defined in terms of the scientific method or the behaviors of scientists, one thing is certain: science is not absolute. At any given time the apparent facts revealed by observations and their interpretation are limited by many factors: the limitations imposed by the state of technology (the quality of telescopes, the ability to travel to the opposite side of the Earth); the influence of the paradigms within which scientists work (the behavioral norms of each sect within science); the danger of seeking to confirm rather than challenge; and the impossibility of dealing with things unknown – “we don’t know what we don’t know” but seldom qualify (or are allowed to qualify) judgment with an admission of ceteris paribus.

From Science To Knowledge To Evidence

Recognizing that science is not absolute is not the same as saying science is junk, to use a term currently in vogue among the detractors of forensic science. Bacon was a champion of science as a tool for the betterment of humankind, and our lives today are shaped by it, from the trivia of the entertainment industry, to the very practical and significant advances in medicine, and the seemingly arcane activities associated with increasing our understanding of the natural world, such as the Large Hadron Collider. In the criminal justice system, the value of science is that it provides evidence that is indisputably more reliable than eye-witness testimony and that provides significant information not otherwise available to the triers of fact. For example, the Innocence Project in the United States (Innocence Project 2011) has identified eye witness misidentification as a leading factor in 75 % of the wrongful conviction cases that it has successfully pursued.

An understanding of the scientific method, and to an extent, how it can produce the knowledge inherent in forensic science, permits an analysis of the purpose of the forensic process, evidence. Although dictionaries define “evidence” in a legal context as something submitted to a court to assist it in arriving at a decision, crime laboratories in the US also use “evidence” synonymously with “exhibit,” namely a physical entity recovered from a crime scene. This research paper avoids that usage, preferring the sequence that an exhibit is something presented before a court, the examination of which has produced evidence that may assist the tribunal in its determinations.

Types Of Forensic Evidence

The legal process distinguishes between real and testimonial evidence, which are respectively evidence resulting from the examination of exhibits and evidence resulting from the direct narrative of a witness as to what he or she has done or observed. Real evidence can be further classified according to the use to which it is put, namely inceptive, exclusionary, corroborative, or associative.

Inceptive evidence is evidence that indicates a crime has been committed. Straightforward examples include detection of accelerant traces at a fire scene and identification of cocaine in someone’s possession. Less straightforward is the finding of semen in samples taken from the vagina of a woman who states that she has been raped, as the evidence speaks to intercourse and not to absence of consent – perhaps a good instance around which to discuss the application of ceteris paribus to forensic science. Identifying semen in intimate samples from the alleged victim, and DNA profiling to link the semen to the alleged assailant is the first and core part of the forensic science investigation of a rape. But is it possible to have rape without semen – the use of a condom, or penetration without ejaculation for example, and possible to have semen identified as being from the suspect but without rape – if the court accepts that the intercourse was consensual or that the semen was from a different act of intercourse that occurred some-time before the act of rape.

Exclusionary evidence is to identity in forensic science as falsification is to hypothesis testing in science in general. There are many techniques available that speak to individual identity: fingerprints; DNA profiles; facial recognition; acquired characteristics such as tattoos, restorative dentistry, and skeletal fractures; and voice. These may be ranked in ascending order of how well they approach the critical test of knowing the identity of someone: voice, facial recognition, acquired characteristics, DNA, and fingerprints. There is a continuum from transient and variable voice, through subjective facial recognition (although computer programs are changing this), to acquired characteristics which may not be individual and unique, to DNA and fingerprints. Even the DNA and fingerprinting may fall short of what could be accepted as indisputable knowledge. The DNA profile maybe partial, and the latent print may be limited in its data content. Even if they are both complete there is considerable debate at present as to the uniqueness of any individual fingerprint, with little information on population frequencies, and in regard to even the extremely rare DNA profiles, some statisticians will argue that if there is a finite probability of something happening then sooner or later, it will (Gettinby 2012).

And of course “we don’t know what we don’t know” – how were the fingerprint or biological fluid rendering the DNA profile deposited? It therefore may be more scientifically sound to follow Popper and to say that if there are differences in DNA profiles or fingerprints, then can safely be concluded that this excludes a given individual as being the source, and if none are observed, then the conclusion is that the target person or object cannot be excluded as being the source.

Some of the most compelling examples of exclusionary evidence have come from the Innocence Project (2011) in the United States. As of March 2011, there have been 267 post-conviction exonerations in the US arising from the application of DNA testing, the first being in 1989. The true suspects or perpetrators were identified in 117 of the cases.

Corroborative evidence is what remains when there is no exclusion. Corroborative evidence is very similar to associative evidence, which seeks to establish the relationship between things – people with other people, people with places, and objects with other objects. Hairs, fibers, paint glass, soil, some examples of impression evidence, are all examples of areas of forensic science that have traditionally contributed to corroborative evidence. They are also areas that are being encountered less and less frequently because of the difficulty of attaching a weight to them, due to the absence of databases to provide reliable frequencies of the different kinds of corroborative evidence in the population.

The difference between exclusionary evidence and corroborative evidence is mirrored in another way of looking at some forensic evidence, namely identification and class characteristics.

Everyday language uses identity and its derivative “identification” to mean “uniqueness” and the act of “assigning a unique identity” to something or someone. This usage does not correspond however to that found in forensic science, which distinguishes between “identification” and “individualization” thus: identification means that items share a common source or possess the same properties, and individualization means coming from a unique source.

The Latin roots of the two clarify the difference: the root of identify (identification) is idem, which means “the same” whereas the root of individualize is individus meaning “not divisible.” However, the distinction is not absolute and just when “same” becomes “unique” can be unclear. For example the mechanisms used to fire a bullet and to extract the spent cartridge case from a gun impart markings on the case; imperfections left on the lands of the gun barrel during manufacture and the relationship of the lands to the grooves can be used to associate spent bullet cases and recovered projectiles with the weapon that fired the round. Some of these such as the number of lands and grooves and their twist are characteristic of all examples of a particular model of gun. Others such as the imperfections created by tools when machining the barrel will be specific to an individual gun of that model. However, wear and tear and further imperfections created by dirt in the barrel mean that the features specific to a particular gun will change in the course of time.

It may be of value to refer back to some of the classic scientific activities of the nineteenth and early twentieth centuries, where some of the advances in science were related to classifications within the natural world, that is, with taxonomy. The taxonomy of forensic science can be reduced to two levels: What? and Which or Who? The question “what is this” together with the question of “who is this” (which one of all of the higher taxonomic level) can be simplified into just one – identity. The answer to the WHAT question will be the correct identification of something as being one of a specified group of things and the answer to the WHO (or which) question will be the correct identification of a unique member within that group.

This differentiation can be illustrated by returning to Popper and his swans. If there is sufficient agreed information to define what a swan is – the highest forensic taxonomic level – then it is possible to test the hypothesis of whether or not something is a swan.

Popper’s example uses one property of “swanness,” color. Note that Popper does not argue that all white birds are swans, but rather that one of the properties of being a swan is to possess white plumage. If the proposition is extended to be “a large waterbird with a long flexible neck, short legs, webbed feet, a broad bill, and all-white plumage” the finding of a bird with all but one of these would have three possible outcomes: the bird would be classified as other than a swan; the bird could be classified as a new species within the Cygnus (swan) genus; or the variant would be dismissed as an anomaly.

The second taxonomic level is to identify which swan – no two will be identical (birds don’t have identical twins), and to do this requires information beyond the core properties. The conclusions are contextual and depend on the question being posed. If the question is “WHAT” is this, then the object is a swan if it possesses the agreed core properties. If the question is akin to “WHO” is this, which swan, then something other than the core properties is required to confirm its individual identity. How much more is one of the major issues in forensic science.

This approach makes it apparent that the question of identity is a matter of graduation on a continuum between identification of class to unique individualization. Between these two points there are an infinite number of degrees of identification, and many opportunities for these to vary with time.

As an example, a tire print is located in the snow at a scene in northern Denmark. A cast is made and the size and general brand of the tire determined. The tread pattern shows uneven wear and an area of damage, probably a cut. Some months later investigators identify a suspect whose car has tires of the same make, and one of which has similar wear and damage patterns. However, because of the amount of driving in the time interval and the problems of capturing fine detail in marks made in snow, there will be differences, at the same time as areas of correspondence between the tire and the print. It is therefore not always possible to conclude that the suspect car is the vehicle involved in the incident, but neither can it be concluded that it is not. This is an example of corroborative evidence that is positioned at an intermediate point in the continuum from what to who.

The above discussion leads to the conclusion that the characteristics of good forensic evidence are:

It should be stable and not change with time.
It should have well defined core attributes and known population statistics.
The basis of variations in non-core attributes should be known and scientifically justifiable. The above discusses the examination of exhibits in the context of the goal of identifying, usually as “WHAT” or “WHO.” There is another framework that is widely used in practice, namely the Locard Exchange Principle and the use of comparison testing. The Locard exchange principle, summarized “as every contact leaves a trace”, is the foundation of traditional associated evidence based on microscopy. The concept is simple and can be illustrated as follows: Mr. A met Miss B in a bar one evening: they knew each other slightly because Mr. A was a friend of a distant relative of hers. The conversation was amicable and Miss B had no problem with accepting Mr. A’s offer to escort her home when the bar closed. The next morning Miss B’s body was found in a river that ran through the park that was on the way between the bar and her home. She had been strangled and raped. This happened some years before the introduction of DNA testing and although blood grouping on the semen from her vagina showed it to be the same as Mr. A’s, it was a group O which is found in 50 % of the population. Mr. A was detained on suspicion and his clothing examined microscopically along with that of Miss B. Fibers found on her coat could have come from the jacket of Mr. A and fibers found on Mr. A’s underpants could have come from the skirt worn by Miss B.

This two-way exchange of fibers is exactly what is entailed by the Locard exchange principle. In considering the weight to be attached to the findings the exchange from the outer clothing is of very little significance given the known and admitted social contact in the bar. However the exchange between the skirt and the underpants is an entirely different matter.

This simple and to some extent simplistic example is taken from a real case in which the author was involved. The complexities of the Locard exchange principle and the reason why it is now not so significant in most laboratory investigations, relate to the dynamics of fiber exchange, loss, and redistribution, to the difficulty of attaching an objective meaning to the relatively few possibly transferred fibers recovered compared to the many orders of magnitude more present from the background population, and to the lack of sound databases regarding the frequencies of the types of fibers encountered.

The question was posed earlier of how much information is required in regard to the move of identity from “WHAT,” or class, to “WHO,” or individualization. The same issue of how much is enough applies to comparison testing. However, the fundamental aspect of individualization is that the core properties that define “WHAT” are known and if they are not present then the person or thing is not a member of the class of interest. Comparison testing does not hinge around these core properties, and professional judgment has to be employed to decide if two items could have come from the same source. This is a major shortcoming in comparative identity.

Beyond What And Who: The Science Behind The Forensic Process

The European Network of Forensic Science Institutes (ENFSI 2002) has defined the Forensic Process by means of a set of standards covering activities from the time of the initial actions at the scene to reporting the results of the investigation and testifying in court. They are:

(a) Undertaking initial actions at the scene of crime

(b) Developing a scene of crime investigation strategy

(d) Assessment of scene of crime findings and considering further examination

(e) Interpreting and reporting findings from the scene of crime

(f) Laboratory examination, testing and presumptive testing

(g) Interpretation of the result of examinations and tests

(h) Reporting from examinations and tests including interpretation of results

The standards involve planning, identifying and preserving potential exhibits, conducting tests, and, at (e) and (g), evaluation and interpretation of what has been done. Considering whether or not these are scientific activities, requires consideration of parts of the section discussing what science is. As discussed by Hald, even though they followed the highly deductive and anthropocentric model of advancing knowledge based on a foundation of accepted societal beliefs, the ancient Greeks and Romans developed the skills of rhetoric to the point at which logic, evidence and argument became refined and effective tools for decision-making. The integral process, due to the Greek rhetorician Hermagoras but described in Latin by St Augustine, is building the argument round the questions quis, quid, quando, ubi, cur, quem ad modum, quibus adminiculis (who, what, when, where, why, how, in what way and by what means/ which aids). These are questions that cannot be answered “Yes” or “No” but demand that explanations based on evidence be given.

Lying at the opposite end of the time frame from the ancients, Thomas Kuhn’s concept that science can be defined as something that scientists do provides a link between social behavior, facts, and rhetoric. Accepting that there is indeed an activity called “forensic science” and that it is conducted by crime scene examiners and chemists and biologists working in places called “forensic laboratories” (and the equivalents of these in the several other subgroups of forensic science described in the introduction), then what happens in forensic science can be measured against the requirements of the scientific method, and the evidence-based objectivity of Hermagoras’ questions, or, simply “The 6 Ws”:

WHAT has happened
WHERE did it take place
HOW did it happen
WHO was involved
WHEN did it happen – at what time and in what sequence
WHY did it happen

The principle underlying the maxim is that each question should elicit a factual answer. What is important is that none of these questions can be answered with a simple “yes” or “no.” They therefore present the incident as a problem to be solved. Solving the problem by providing factual answers to each dimension – each question – is the purpose of investigative inquiry.

The 6Ws define a process (of inquiry) to be used within a process (the ENFSI forensic process), and can be related back to the discussion on the types of evidence that forensic science can furnish. The examples below are from scene examination, because this is the place where Peirce’s surprising event begins, and abduction is a necessary part of the process. However, the same principles apply in all stages of the forensic process.

Inceptive evidence was discussed in relation to information regarding specific crimes (arson and drug possession). The first of the 6Ws – What? – is a broader exposition of inceptive evidence. Was a crime committed or not, and if so, was it planned or accidental? In many cases this may appear to be a trivial matter – a body concealed in a shallow grave, with a gunshot wound to the temple. Or a husband calls, pretty agitated. His wife has fallen from the fourth floor window. Ambulance and police are dispatched to the scene and find her lying dead on the footpath, wearing underwear, socks, pants, sweater and rubber gloves of the type normally used for household cleaning activities. She had several injuries that could have been due the fall from the window.

Applying ceteris paribus to these cases suggests that the first demands to be treated as murder and the second as accident. But “we don’t know what we don’t know,” and have to challenge the hypotheses. In the apparent murder, the questions of how did the body get there, who else was involved, and why all had to be pursued and led to the discovery that it was a case of suicide and concealment of the body. The murder hypothesis was falsified by exclusionary evidence, when it was shown that the blood patterns and bullet trajectory at the scene where the shooting occurred – not where the body was found – could only have arisen from a self-inflicted shot. The accident hypothesis in the other case was firstly challenged by finding blood inside of the gloves – a surprising event – that led to the discovery of widespread residues of blood in the shower in the house, providing corroborative evidence to the conclusion of murder and not accident. The woman had been bludgeoned to death by her husband.

The murder/suicide case also demonstrates one aspect of the second of the 6Ws – Where? Knowledge of where the incident took place is essential in any investigation. It establishes the boundaries within which to search for evidence and can lead to other layers of interest, for example to the primary scene in the first case above.

The 6 W question of “How did it happen” is both obvious and hidden in the murder case, obviously by a fatal gunshot but hidden that it was self-inflicted. The case of the fallen wife illustrates a different aspect of “How” since the injuries themselves could be explained by the fall, and it was the additional information from the blood inside in the glove – exclusionary or falsifying information in regard to the accident hypothesis – that led to the correct conclusion.

“Why” is the most intangible of the 6Ws. It is perhaps less valuable in recreating events than in bringing a sensible closure to a case. In the suicide/concealment case, the deceased shared a house with others who like him were illegal migrants. His friends found him dead when they returned from work and feared the consequences of reporting the death, hence the concealment of the body.

If It Is Science, Does It Matter?

The development of a sustainable description of what science is – the scientific method and its modern refinements – together with the rigorous scrutiny of the steps in the forensic process using the ancient tool of rhetoric transcribed into the 6Ws, establishes forensic science as being a well-grounded scientific discipline. The question was not properly addressed in the NAS report but set aside in favor of a discourse on methodologies and statistical interpretations. Unlike the NAS committee, the US Supreme Court did try to come to terms with “science” in Daubert –vMerrel Dow, as did others. However, both made the mistake of assuming that “scientific” somehow meant “reliable and absolute.”

This paper is about the scientific basis of forensic science. The first part shows how science is not absolute but is ever-evolving and contextual. Lakatos remains the thought leader in both areas. The limitations that ceteris paribus places on the formulation and evaluation of hypotheses have been described, but Lakatos was also a strong proponent that taking a broader view of Popper’s ideas of falsification is a vital part of the advancement of science. He created the concept of research programs to describe how exploration of real and apparent falsifications strengthen by providing a framework for the continuous iteration of ideas and refinement of knowledge. And so it should be with forensic science, the formulation of a hypothesis and its challenge, and the understanding that falsification of the initial hypothesis is not an end but a beginning, as new testing and a new examination of the existing information leads to a better hypothesis that perhaps approaches knowledge.

However, two vital parts of the work of the forensic scientist are the reliability of the testing methods and the validity of conclusions drawn from observations and tests. These have nothing to do with science any more than the quality of the prosecution or defense in a trial have. Quality assurance in chemical, biological and physical testing is a well-worked topic (Tilstone 2012), not covered here, but are dealt with in the NAS report somewhat (but not entirely) better than it dealt with science.

A more subtle issue is that of confirmation bias. It has long been a tenet of forensic science that findings based on observation, that is, findings that are subjective, must be confirmed by an independent observer to add a degree of objectivity. The matter of objectivity has been dealt with as an element in quality assurance, by the definition of “Objective test” and a description of how to ensure objectivity in the guidance document for forensic accreditation (ILAC 2002), but recent work shows that the confirmation itself can be subjective, and systems approaches have been proposed to overcome the problem (NIST 2012). Aside from subjectivity and the breakdown (or lack of implementation) of quality assurance procedures, bias is an inevitable consequence of an inductive approach based on asking a question that can be answered “Yes” or “No” and a rigorous implementation of the 6Ws together with effective quality assurance and a more systems approach to observer-dependent testing should resolve the problem.

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