A Philosophy of Crime Scene Reconstruction
The Association for Crime Scene Reconstruction (2012) defines the purpose of crime scene reconstruction: "To gain explicit knowledge of the series of events that surround the commission of a crime using deductive reasoning, physical evidence, scientific methods, and their interrelationships." The crime scene is a static representation of a dynamic event. The evidence found following the commission of a crime is the culmination of everything that occurred over the course of time during which the crime took place. The crime scene, thus, has four dimensions: width, depth, height and time.
Chisum and Turvey (2007) explain that "the crime scene is a dynamic location; it does not remain virginal or static, as a 'frozen moment of time,' but rather it is constantly subject to change. The greater the time interval between the crime, the documentation, and examination of the scene, the greater the changes may be" (p. xviii). The deposition of evidence at a crime scene is a mechanical process controlled strictly by the laws of physics commonly applied in engineering practice. The forensic engineer thus operates with the foundational tools needed to fully examine, analyze, and interpret the processes by which items of evidence have been deposited at a crime scene.
While many in the legal world are unfamiliar with the science of crime scene reconstruction and believe it to be a relatively new discipline, in fact, crime scene reconstruction has a rich history dating back to at least the first half of the 19th century. Perhaps the best treatment of the history of crime scene reconstruction appears in Chisum's and Turvey's Crime Reconstruction; rather than attempting to rehash what has already been written, this text will refer the reader to appropriate references (Chisum & Turvey 2007, pp. 1-35; Gardner & Bevel 2009, pp. 4-8). Familiarity with the history of crime scene reconstruction will be necessary for the testifying reconstructionist to effectively deal with challenges that the practice is not scientifically reliable in an effort to exclude testimony regarding the crime scene reconstructionist's findings. Crime scene reconstruction is scientifically reliable as long as it is properly carried out. It is not a new and novel technique.
Crime scene reconstruction is an application of forensic science; in fact, the work of every forensic scientist is a contribution to crime scene reconstruction in toto. A true crime scene reconstructionist is a forensic scientist, but not every forensic scientist is a crime scene reconstructionist. It is important to understand who a forensic scientist is. Chisum and Turvey (2007) provide these defintions (p. xvii):
A scientist is someone who possesses an academic and clinical understanding of the scientific method and the analytical dexterity to construct experiments that will generate the empirical reality that science mandates. A forensic scientist is one who is educated and trained to examine and determine the meaning of physical evidence in accordance with the established principles of forensic science, with the expectation of presenting her findings in court.
Dr. Max Houck (2011) argues that forensic science is a separate basic science, rather than simply an applied science, because "it deals with topics and combinations of topics that no other science does." Houck defines forensic science as "the science of spatial and temporal relationships between people, places, and things involved in crimes." Forensic science, much like geology, astronomy, archeology, and paleontology, is a historical science that deals with proxy data. "The events under study have already occurred and are in the past," Houck explains. "A forensic scientist does not view the crime as it occurs [but] must assist the investigation through the analysis of the physical remains of the criminal activity."
The crime scene reconstructionist deals in time periods that are much shorter than most other scientists relying on proxy data, but he or she must also deal in details that are significantly more fine. The archeologist, for example, may deal in time spans of hundreds or even thousands of years, but will likely be dealing in much grosser detail than the forensic scientist. The archeologist will view the collective actions of a group whereas the crime scene reconstructionist will view the minute actions of individuals. "Because of this abstraction," Houck (2011) explains, "we can only test hypotheses about what could have produced the proxy data we see. We cannot test the actual events that did produce that data." Hence, we meet one of the limitations of crime scene reconstruction: that definitive conclusions are often beyond our grasp. We are limited, as Houck explains, by the asymmetry of time: the past cannot be undone.
The crime scene provides a snapshot of what took place, frozen in time, the culmination of a series of events that occurred over the course of seconds, minutes, hours, and even days. The asymmetry of time tells us that what we have found at the crime scene was collected in sequence from first to last, and we must unravel that sequence, generally working backward from last to first. But our snapshot does not begin when the criminal first enters the scene and end when he leaves. Instead, our snapshot includes data that were there perhaps long before the arrival of the offender, and it likewise includes changes to the scene and evidence that have occurred during the interval of time from when the criminal fled the scene to when the crime is investigated. Even if the scene has been undisturbed by people or animals, during that time changes occur. Much like a faded old photograph found in a box in one's closet, evidence that once was clear can be become muddled.
While crime scene reconstruction is a forensic science discipline, the crime scene reconstructionist need not be an expert in every facet of forensic science. Chisum and Turvey (2007) argue for a more generalist approach writing: "[W]e do not propose that to perform crime reconstruction one needs to be an expert in all forensic disciplines. We propose that forensic reconstructionists must become an expert in only one: the interpretation of the evidence in context" (p. xviii, emphasis in original). To be sure, the crime scene reconstructionist must be a crime scene expert; without knowledge of, and experience processing, crime scenes, one's ability to interpret the evidence in context is almost surely lacking. But there is more to the process than just having experience processing crime scenes. Without a broad-based knowledge of the technical aspects of forensic evidence, without an investigative background, without strongly understanding the motivations and behavior of those who commit crimes, the would-be reconstructionist is unlikely to succeed.
Gardner and Bevel (2009) offer three qualities necessary for one to be a crime scene reconstructionist:
- an understanding of general forensic science;
- "direct and specific" experience dealing with crime scenes; and,
- the "ability and willingness to be objective" (p. 13).
French criminologist and forensic science pioneer Dr. Edmond Locard developed the founding principle of forensic science, which has become known as the Locard Exchange Principle: every contact leaves a trace. Locard theorized that whenever a person commits a crime, that person leaves behind some item of evidence at the crime scene that was not there prior to the suspect's arrival, and, likewise, takes away something that was there before. Such exchanges take place during almost any contact between one object and another, or between a person and an object (Chisum & Turvey 2007, pp. 20-25; James & Nordby 2009, p. 169; Fisher 1993, p. 165). To be sure, Locard's Exchange Principle is at the heart of crime scene reconstruction. "[T]he incorporation of this principle into evidentiary interpretations," writes Chisum and Turvey, "is perhaps one of the most important considerations in the reconstruction of crime” (p. 25). Considered by many to be the father of modern criminalistics, Paul Kirk (1974) wrote (p. 2):
Wherever he steps, whatever he touches, whatever he leaves--even unconsciously--will serve as silent evidence against him. Not only his fingerprints and his shoeprints, but also his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen that he deposits or collects--all these and more bear mute witness against him. This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because witnesses are. It is factual evidence. Physical evidence cannot be wrong; it cannot perjure itself; it cannot be wholly absent. Only in its interpretation can there be error. Only human failure to find, study, and understand it can diminish its value.
While Locard's Exchange Principle is foundational to crime scene reconstruction, it must not be so construed as to mean that, if no evidence of an event was found, the event never happened. The oft-used phrase, "the absence of evidence is not evidence of absence," while hotly debated as a matter of science and philosophy, sums up conceptually how one should carefully approach the reconstruction of criminal events. Clearly, there is a difference between a lack of evidence after careful searching, study, and research and a lack of evidence due to a deficiency of research, insufficient study, or a poorly executed crime scene search. We must recognize that our ability to interpret evidence is necessarily limited by our ability to find evidence. DNA evidence that was once unheard of can now offer definitive association to a donor. New techniques for developing fingerprints lead to association between a donor and an item of evidence that was previously processed with no latent fingerprints being found. Dr. Houck (2011) provides a good explanation: "When two items come into contact, information may be exchanged; this exchange of information occurs, even if the results are not identifiable or are too small to be found."
In some cases, there simply are not enough pieces to see what the puzzle is supposed to look like. Not every crime can be solved, nor can every crime scene be reconstructed. O'Hara and O'Hara (1988) explain (p. 6):
It is a common misconception that every crime is intrinsically soluable; that there is always sufficient evidence available to reveal the identity of the criminal; that the perpetrator always leaves traces at the crime scene which, in the hands of a discerning investigator or technician, will lead inevitably to his door. It is for this reason that a citizen who cannot determine which of his three children opened a forbidden jar of cookies may become indignant at the inability of his police force to locate unerringly the perpetrator of a mysterious robbery among the several million inhabitants of his city.
Crime scene reconstruction is an organized, logical process of arriving at proper, scientifically supported conclusions about the events surrounding the creation of the crime scene being examined. Crime scene reconstruction must be performed methodically. The crime scene reconstructionist seeks to analyze the items of evidence--both deposited and removed--and apply an ordered, logical method that will result in the determination of event sequences that, in turn, lead to a clear picture of what occurred during the commission of the crime. The process has been described as similar to putting together a jigsaw puzzle without having access to the box top: the practitioner does not know what the picture is supposed to look like, and, in most cases, does not even have all of the pieces. However, a seasoned crime scene reconstructionist who utilizes a strongly methodical approach can usually recreate the picture in enough detail that he or she can make the picture clear.
Crime scene reconstruction is a process of logic. It is the assemblage of scientific and investigative data into a coherent representation of past events. The pieces are put together; the picture is formed, at least enough of the picture that the missing pieces may be interpolated. Logic is at its root. The crime scene reconstructionist must strive to apply proper logic and well-founded reason that is as free from bias as is humanly possible. "The use of correct reasoning processes," write O'Hara and O'Hara (1988), "must be learned by conscious application, and constant vigilance against the pitfalls of false premises, logical fallacies, unjustifiable inferences, ignorance of conceivable alternatives, and failure to distinguish between the factual and the probable" (p. 20).
Crime scene reconstruction employs both deductive and inductive reasoning to answer questions associated with the commission of a particular crime. Deductive reasoning is the process of moving from the general to the specific. A deductive statement might read as follows: "Fingerprints can only be deposited on an item if the donor touches that item. The suspect's fingerprints are on the window; therefore, the suspect touched the window." As long as the base principle is valid, the conclusion is likewise valid. Inductive reasoning, however, moves from the specific to the general. Inductive reasoning, while necessary and useful for crime scene reconstruction, must be carefully employed, and it generally leads to statements of probability rather than certainty. Osterburg and Ward (1992) explain: "[C]onsider the man who notes that of the 10 species of bird he observed, all are able to fly. When he induces from this observation that all birds fly, he will be incorrect" (pp. 12-13). In fact, there are numerous species of birds that do not fly.
To make scientific study of criminal matters a valid fact-finding tool, it must be based on a proper understanding of the underlying physical, physiological, and psychological phenomena. Supposition must be replaced by critical study of the evidence. To accomplish this type of analysis, practitioners rely on substantive research. That research, unfortunately, is not always readily available. A committee of the National Academy of Sciences issued a report that was, in many ways, strongly critical of the current state of forensic science. One of the committee's major criticisms was the paucity of research on which forensic science has relied. "The simple reality is that the interpretation of forensic evidence," the committee wrote, "is not always based on scientific studies to determine its validity" (Committee 2009, p. 8). The committee does, however, clarify one issue important to crime scene reconstruction: that the value of forensic evidence is directly proportional to the context in which the evidence is viewed. "In evaluating the accuracy of a forensic analysis, it is crucial to clarify the type of question the analysis is called on to address," the committee writes, addressing identification evidence. "Thus, although some techniques may be too imprecise to permit accurate identification of a specific individual, they may still provide useful and accurate information about questions of classification" (p. 8). This concept is equally true of crime scene reconstruction. Precise evidence leads to precise conclusions; imprecise evidence leads to imprecise conclusions, but not useless ones. This distinction is critical to the understanding of crime scene reconstruction as a process. Practitioners need not be limited by the constraints of definition. Unknowns have been dealt with in science for millennia, yet scientific progress has not slowed. Successful scientists have embraced the unknowns, understood their effect on analysis, and used them to define the limits of the science and guide scientists in pushing the envelope.
In reconstructing crime scenes, the practitioner seeks answers to certain fundamental questions:
- What happened?
- Where did it happen?
- How did it happen?
- When did it happen?
- Who was involved?
- Why did it happen?
The process of crime scene reconstruction is often viewed as a physical evidence problem, and in many ways it is, which means that we tend to be less interested in "why" than we are in the other questions. However, crime is ultimately a human act, and no reconstruction of a human act can be wholly separated from the underlying human behavior. "All criminal investigation is concerned with people and with things," writes Kirk (1974). "Only people commit crimes, but they invariably do so through the medium of things" (p. 1). Those who have studied criminal profiling techniques recognize, however, that the criminal psyche--and thus his "signature"--is strongly related to the crime scene evidence. In fact, the crime scene is where the profiler begins his work. It is not possible to adequately perform the crime scene reconstruction task without considering all aspects of the crime involved. All of the known facts must be considered. The criminal's motivation and mindset must be viewed as part of the reconstruction process.
Some argue that forensic scientists should not concern themselves with why; to do so, they claim, biases the scientist's perspective. "In crime scene analysis," write Gardner and Bevel (2009), "the 'why' of crime is the analyst's event horizon; physical evidence simply does not allow us to objectively explain the why of human behavior" (p. 3). Chisum and Turvey (2007) explain that "psychological evidence" is "more commonly the province of the criminal profiler and the behavioral scientist" (p. 142). But this view denies the ultimate goal of forensic science: to get a clear picture of what happened. The "why" is necessarily a part of that picture. What if, for example, the work of the forensic scientist determines that a car's windshield was fogged obscuring the driver's view? Could that explain why the driver ran over the darkly dressed pedestrian? Could the fact that a shooter's perception-reaction time is at least as great as the time needed for a person to turn 180 degrees explain why the person was shot in the back despite the fact that the shooter claims to have fired when the person was facing toward him? Certainly there are numerous occasions when forensic science is called upon to answer the question "why", and this question is knitted into the fabric of what the crime scene reconstructionist does.
Crime scene reconstruction is a scientific, logical method of reaching conclusions about the six fundamental questions based on certain inferences that may be drawn from the known facts. Very seldom will the practitioner be able to reach definitive, clear-cut answers that are unencumbered by any degree of uncertainty. Crime scene reconstructionists often deal in probability rather than certainty. However, when the practitioner takes all known facts into account with a clear head and open mind, he or she is often able to reach valid, usable solutions to crime scene problems.
A crime scene is a puzzle. The crime scene reconstructionist's job is to put the pieces of the puzzle together in order to see the picture. Unfortunately, in so doing we have two significant problems to overcome: (1) we do not know what the picture is supposed to look like and (2) we rarely have all of the pieces. The quality of a crime scene reconstruction is proportional to the number of available pieces. If enough pieces exist that the gaps in the picture can be effectively interpolated, then a proper crime scene reconstruction can be performed. The more pieces that are known, the more complete the picture. "We only get the bits and pieces leftover after the event occurs," explains Dr. Houck (2011). "We don't get to choose our data a priori."
The resolution of the crime scene data may be quite good or it may be quite poor. Distinguishing signal from noise presents tremendous challenges to the crime scene reconstructionist. "Crime scene processing," explains Dr. Houck (2011), "is essentially an exercise in judgment, bulk, and random sampling." At a homicide scene inside a house, for example, the crime scene investigator must determine what within that house belongs there and thus has no evidentiary value and what has either been brought to the scene or altered in some way as to give it evidentiary value. Those items with evidentiary value are signal; those without are noise. Collecting too much evidence buries the signal in noise; collecting too little leaves valuable signal behind. Deciding where to draw the line is an exercise in judgment.
No matter what information exists, however, the overriding factor that should be foremost in the mind of a crime scene reconstructionist is the belief that whatever crime scene reconstruction is performed is only as good as the context in which it is considered. A successful crime scene reconstruction must take into account all of the available evidence, whether physical, testimonial, or documentary. The evidence considered should include, but not be limited to:
- physical evidence;
- victim statements;
- witness statements;
- suspect statements;
- motivational/behavioral/psychological evidence;
- documentary evidence; and,
- common sense.
In reviewing the various types of available evidence, it must be understood that testimonial evidence may be biased by such factors as the witness's point-of-view, his life's experience, his knowledge and education, his observational skills, and his relationship with the parties involved in the crime. Witnesses often jump to conclusions based on emotional factors rather than arriving at sound, logical conclusions upon which the investigator must rely. When testimonial evidence is elicited from suspects, it is clear that the information gleaned is unlikely to consist of the whole truth. It is important, nonetheless, for the crime scene investigator to pay careful attention to a suspect's statements as important information can be gleaned from those statements to help guide the direction of a crime scene investigation. It is the rare case that an offender is able to fabricate a story that contains no pieces of the truth whatsoever; often a suspect's confession will contain details that are true and are physically verifiable. In addition, those elements of a suspect's story that can, through proper analysis of physical evidence, be proven false serve to refute the suspect's story, damage his credibility, and establish his consciousness of guilt.
Crime scene reconstruction is an organized, logical process of arriving at proper, scientifically supported conclusions about the events surrounding the creation of the crime scene being examined. Crime scene reconstruction must be performed methodically. Crime scene reconstruction can be divided into three distinct phases:
- Investigation: The crime scene is documented and examined for physical evidence without respect to the significance of that evidence. It is during this phase that photographs are taken, measurements are obtained, searches are conducted, interviews are performed, and information is gathered. At this stage, the crime scene analyst should avoid formulating theories about how the crime took place so as not to bias later judgments during the subsequent phases of the crime scene reconstruction process or limit his desire to seek additional evidence.
- Analysis: Individual items of evidence, or groups of a particular type of evidence, are examined analytically to determine what information they tell us. This phase deals primarily with physical phenomena and scientifically provable facts. An example of the analysis phase would be the determination that a fingerprint found on a drinking glass belonged to John Doe; we would not conclude at this point that John Doe committed the crime, or even that he actually drank anything from the glass.
- Reconstruction: All of the evidence, including testimonial and other non-physical evidence, is viewed as a whole so that events surrounding the creation of a crime scene can be determined. This phase may deal in probabilities rather than known facts. Psychological and behavioral evidence may be considered. During the reconstruction phase, all of the available puzzle pieces are put together.
Crime scene reconstruction involves two processes:
- Eliminating those possible events that physical evidence proves did not happen;
- Determining those events that physical evidence proves did happen.
The process is not dissimilar to the manner in which a physician goes about diagnosing a medical ailment. In most cases, symptoms present in combinations that are not unique to one particular disease. The physician, thus, must go about eliminating diseases until the correct diagnosis is achieved. Through testing, x-rays, magnetic resonance imaging, blood tests, and other procedures, the treating physician goes through the list of applicable diseases until he can confidently diagnose the ailment. In some cases, a positive diagnosis is made, but in many cases, diseases are eliminated from the list until only one is left. Most often, this process is accomplished by starting with the diseases that are simplest to rule out and working progressively toward those that are more difficult to diagnose.
One important pitfall that must be avoided for successful crime scene reconstruction is the tendency to allow one's thinking to be restricted by preconceived notions and biases about the investigation at hand. Such notions tend to lead to confirmation bias in which a crime scene reconstructionist pursues evidence that tends to prove a particular theory while ignoring evidence that tends to disprove it. A critical concept of science in general and forensic science in particular is that of falsification. The difficulty with proving that an event occurred is that one rarely knows the standard of proof: how much evidence does it take to prove, for example, that a death was a homicide and not a suicide? There is no clear-cut answer to that question, and, hence, no clear-cut solution to the problem. Scientifically we avoid the tendency toward confirmation bias by establishing all reasonable possibilities and then working one-by-one to disprove them. When all but one possibility can be disproved, the one remaining possibility becomes the solution to the problem. Chisum and Turvey (2007) explain: "A scientist knows that confirmation of one's theories is easy to find, especially if that is all one seeks. Good science is not about trying to prove one's theories but, rather, working tirelessly to disprove them through falsification" (p. xvii, reference omitted).
Former FBI profiler John Douglas explains the problem well when he refers to the "groupthink" tendency in which individual concerns that investigators have with respect to a case are often stifled by the overall thinking process of the group (Douglas & Olshaker 2000). Douglas writes that the investigator must resist the tendency to make the facts fit his notion of the case rather than letting his notion of the case fit the facts. When dealing with a crime scene, it is important to have the ability to "think outside the box," so to speak. What often happens is that if the investigator is dispatched to, say, a suicide, then he evaluates the scene as if it must be a suicide, trying all the while to demonstrate that it is a suicide rather than being open to the possibility that it may be something else. Currently, "groupthink" tendencies adversely affect the crime scene reconstruction field because many scientific myths have pervaded the field. If one applies a standard, organized approach to crime scene reconstruction, the tendency to be swayed by "groupthink" fallacies will be greatly reduced. Preconceptions about the outcome of a case should be all but eliminated in favor of a more objective view in which all crime scenes are, at least essentially, treated equally.
A solid crime scene reconstruction is built on the culmination of all available evidence, physical and testimonial. It involves many disciplines within forensic science. It is the reconstructionist's job to assemble the pieces and get a good view of what the puzzle looks like. Chisum and Turvey (2007) explain that "no one discipline can truly stand alone in a reconstruction. Each form of evidence must be in agreement with the other forms that are present. Each part must be meticulously established and then considered not just on its own but also in its place as part of the greater whole. What is it, how does it fit, and what does it mean in context—these are the questions asked by a reconstructionist" (p. xix).
Remember: CONTEXT is paramount.
Crime scene reconstruction is a scientific, logical method of reaching conclusions about the six fundamental questions based on certain inferences that may be drawn from the known facts. Very seldom will we be able to reach definitive, clear-cut answers that are unencumbered by any degree of uncertainty. We often deal in probability rather than certainty. However, when we take all known facts into account with a clear head and open mind, we are often able to reach valid, usable solutions to crime scene problems.
One method for balancing uncertainly against the usefulness of our conclusions is to narrow our frame of reference from broad, complicated questions to simpler, more direct ones. For example, in an equivocal death investigation, it is easy to be overwhelmed by the question: Is this a homicide or a suicide? Instead, we will find it simpler to ask, for example: Is this a self-inflicted gunshot wound? By answering the more direct question, we have by implication answered the broader question. If the gunshot wound was self-inflicted, the death is a suicide (or possibly accidental); if however, we determine that it was not self-inflicted, the death is a homicide.
As we work toward answering our reconstruction questions, we must do so by following some logical, scientific "checklist" of sorts. We call this the scientific method.
Association for Crime Scene Reconstruction. 2012. Website, accessed January 6, http://www.acsr.org.
Chisum, W., and Turvey, B. 2007. Crime reconstruction. Burlington, MA: Academic Press.
Douglas, J., and Olshaker, M. 2000. The cases that haunt us. New York: Scribner Books.
Gardner, R., and Bevel, T. 2009. Practical crime scene analysis and reconstruction. Boca Raton, FL: CRC Press.
Houck, M. 2011. "A philosophy of forensic science." Presentation at the FDIAI/GDIAI Joint Educational Conference, Panama City Beach, FL, 24 October.
James, S., and Nordby, J., eds. 2009. Forensic science: An introduction to scientific and investigative techniques. 3rd ed. Boca Raton, FL: CRC Press.
O'Hara, C., and O'Hara, G. 1988. Fundamentals of criminal investigation. Rev. 5th ed. Springfield, IL: Charles C. Thomas.
Osterburg, J., and Ward, R. 1992. Criminal investigation: A method for reconstructing the past. Cincinnati, OH: Anderson Publishing Co.
Michael Knox is a forensic consultant and is the owner of Knox & Associates, LLC , a Jacksonville, Florida-based forensic consulting company that specializes in firearms, ballistics, and crime scene reconstruction. He was a police-officer/detective with the Jacksonville Sheriff’s Office for over 15 years having worked in patrol, DUI enforcement, crime scene investigations, and traffic homicide investigations. He was the training coordinator for the agency’s crime scene unit for several years and has provided crime scene training in Peru, the United Arab Emirates, the Republic of Georgia, and around the United States. He has testified as an expert witness in crime scene reconstruction in state and federal courts in Florida, Alabama, Texas, and Illinois. He holds a Bachelor of Science degree in mechanical engineering from the University of North Florida and Master of Science degree in forensic science from the University of Florida. He also holds current certification as a crime scene reconstructionist through the International Association for Identification and accreditation as a traffic accident reconstructionist through the Accreditation Commission for Traffic Accident Reconstruction.