W. Jerry Chisum, BS1; Brent E. Turvey, MS2
Title: "Evidence Dynamics: Locard's Exchange Principle & Crime Reconstruction"
Reference: Chisum, W.J., & Turvey, B. "Evidence Dynamics: Locard's Exchange Principle & Crime Reconstruction," Journal of Behavioral Profiling, January, 2000, Vol. 1, No. 1
Abstract: Conclusions regarding the circumstances and behaviors elicited from the physical evidence related to a crime (crime reconstruction) can infrequently be housed within the confines of absolute certainty. This paper discusses the development of Locard's Exchange Principle and historical and contemporary philosophies surrounding crime reconstruction. It further discusses the fallacy of assuming the integrity of physical evidence, and provides a logical foundation for the concept of Evidence Dynamics. Evidence Dynamics refers to any influence that changes, relocates, obscures, or obliterates physical evidence, regardless of intent. Evidence Dynamics, it is further argued, come into play during the interval that begins as evidence is being transferred, and ends when the case is ultimately adjudicated. A discussion of the various types of Evidence Dynamics is provided, followed up by demonstrative examples from the authors' case files.
1W. Jerry Chisum has been a criminalist since 1960. In October of 1998, he retired from 30 years of service with the California Department of Justice into private practice. He is currently serving as Vice-President of the Academy of Behavioral Profiling, and is a member of their Board of Directors. He can be reached for comment or consultation by contacting: URL: www.ncit.com; firstname.lastname@example.org
2Brent E. Turvey, MS is a forensic scientist, criminal profiler, and a full partner of Knowledge Solutions, LLC. He is currently serving as Secretary of the Academy of Behavioral Profiling, and is a member of their Board of Directors. He can be reached for comment, consultation or reprints of this article by contacting: Knowledge Solutions, 1961 Main St., PMB 221, Watsonville, CA 95076; Phone (831)786-9238; email@example.com.
Of all responsibilities shouldered by the forensic scientist, the reconstruction of the circumstances and behaviors involved in a crime is one of the most important. In conjunction with agreeable witness accounts, a crime reconstruction may be a powerful instrument of corroboration. In the face of conflicted witness accounts, it may provide an objective view that points to one possibility over another. In the absence of witness accounts, it may be used to investigate and establish the actions that occurred at the scene of a crime. The role that crime reconstruction can play investigatively and legally should never be underestimated.
Because of the varied evidence and circumstances involved, the ability to reconstruct crime requires broad forensic knowledge, an objective if not conservative disposition towards the examination and interpretation of evidence, and what the fictional Dr. Watson of Sherlock Holmes fame referred to as a "peculiar facility for deduction." 
Despite its importance to investigative and legal venues, crime reconstruction is often performed inappropriately by the unknowledgeable and overconfident. This includes those with little knowledge of, or training in, the peculiarities of physical evidence and the forensic sciences. Those testifying as experts in the area of crime reconstruction routinely cite as a premise, for otherwise unproven opinions, the sum of their education, training, and experience. It may be the case that this is offered in the place of facts from the case file. This practice is regarded as illegitimate for a forensic examiner. "Experience should not make the expert less responsible, but rather more responsible for justifying an opinion with defensible scientific facts." 
Conclusions regarding the circumstances and behaviors elicited from the physical evidence related to a crime can infrequently be housed within the confines of absolute certainty. It is often an intensive process with imprecise results containing evidentiary holes, sequential gaps, and alternate possibilities. This does not suggest that crime reconstruction efforts lack investigative or legal utility. The utility of crime reconstruction is by no means bound to any predisposition for certainty. Rather, its utility is more often found in establishing the general circumstances of a crime, demonstrating links between victims, suspects, and offenders, corroboration of witness statements, providing investigative leads, and identifying potential suspects. 
Further still, it is often the case that what the physical evidence excludes, fails to establish, or equivocates, is actually of great investigative and legal importance. Forensic analysis in general, and crime reconstruction in particular, is concerned with those conclusions that can be logically drawn from the evidence, as well as with those that cannot. As such, the consideration of both the strengths and limitations of available physical evidence are an important part of crime reconstruction. It is with these considerations in mind that we begin our discussion of the relationship between Locard's Exchange Principle, Crime Reconstruction, Evidence Dynamics and their implications to forensic examinations.
The Development of
Locard's Exchange Principle
Bertillon was motivated to develop his methods not only by the desire to assist in the tracking of criminals and their behavior, but also by a personal belief that everything that "lived and moved under heaven" was somehow unique . His was something of a radical notion in criminal investigation at the time: that science and logic should be used to investigate and solve crime. As Msr. Bertillon's biographer stated:
Bertillonage was employed to identify criminals by law enforcement for at least two decades, until it was replaced by the use of fingerprints. In 1891, Dr. Hans Gross, an Austrian Magistrate and Professor of Criminology, made the following observation, "The advantages of finger-prints over the Bertillon system have become so well established that the latter can with perfect safety be dispensed with altogether as unnecessary for the purposes of identification."
However, Bertillonage was not the limit of Msr. Bertillon's contribution to the forensic sciences, nor was it his most significant. His dedication to precise measurements and the use of photography led to a combination of the two practices beyond criminal identification. Bertillon assisted in the development and practice of forensic photography by introducing a measuring scale with the persons and objects of evidence that he photographed . The usefulness of this practice soon became apparent. He was routinely sent out with investigators to document crime scenes. He would photograph the bodies of victims, their relationship to significant items of evidence in the scene, as well as the position, size, nature and extent of other physical evidence including footprints, stains, toolmarks, and points of entry . Until the development of this practice, criminal investigators and the courts relied upon sketches and notes of varying precision for their understanding of the context of a crime. That is, if any record were made of a crime scene at all.
Bertillon also instructed and influenced several students, including Dr. Edmond Locard, whose work formed the basis for what is widely regarded as a cornerstone of the forensic sciences, Locard's Exchange Principle (for discussion, see: ,  & ). Dr. Locard, like Dr. Hans Gross and Msr. Bertillon before him, advocated the application of scientific methods and logic to criminal investigation and identification . As stated by Dr. John Thornton, a criminalist and a former professor of forensic science at the University of California, Berkeley:
Due in no small part to Mr. Bertillon's influence, it was Dr. Locard's belief and assertion that when any person comes into contact with an object or another person, a cross-transfer of physical evidence occurs . By recognizing, documenting, and examining the nature and extent of this evidentiary exchange, Locard observed that criminals could be associated with particular locations, items of evidence and victims. The detection of the exchanged materials is interpreted to mean that the two objects were in contact. This is the cause and effect principle reversed; the effect is observed and the cause is concluded.
Forensic scientists also recognize that the nature and extent of this exchange can be used not only to associate a criminal with locations, items, and victims, but with specific actions as well [2, 3, 11, 13, 14].
Modern methods of crime reconstruction owe themselves to a strong history marked by rigorous analytical thought and forensic application. The collective work of Alphonse Bertillon, Dr. Hans Gross, and Dr. Edmond Locard are no small part of this history. Enduring themes include the importance of physical evidence, objectivity, the necessary employment of logic, and viewing witness, victim, and offender statements with suspicion.
Just before the turn of the century, Dr. Hans Gross, in discussing how a crime should be reconstructed, argued for strict objectivity and a logical, sequential, frame by frame analysis on the part of criminal investigators:
Dr. Gross also decried the heavy reliance of criminal investigators and the courts on witness accounts, strongly advocating the use of physical evidence, writing:
Dr. Edmond Locard, in speaking similarly on the subject of physical evidence and crime reconstruction, maintained that:
Dr. Theodore Reik, a Professor of Psychoanalysis at Vienna University, an early disciple of Dr. Sigmund Freud, also argued for the use of objectivity and logic in the investigation of crime and criminals:
In the second half of this century, the late Dr. Paul Kirk, Professor of Criminalistics at the University of California, Berkeley, shared the views of Drs. Gross and Locard regarding issues of witnesses, physical evidence, and crime reconstruction, arguing:
Dr. Kirk further argued, supporting the validity of Locard's Exchange Principle, the importance of transfer evidence to crime reconstruction:
However, Dr. Kirk also argued for caution in the interpretation of evidentiary exchanges. In this brief discussion on establishing the identification of an object's source, he makes it clear that it is an endeavor with inherent hazards under even the best conditions.
Dr. Henry Lee, former Director of the Connecticut State Police Crime Laboratory, also advocates a combination of both physical evidence and logic by forensic scientists engaging in reconstruction:
Dr. John Thornton, previously mentioned, a student of Dr. Kirk, describes the mechanics of the logic that should be employed by forensic scientists when undertaking a forensic examination:
Criminalist Dr. Richard Saferstein, retired Chief Forensic Scientist from the New Jersey State Police Lab, also argues:
One of the authors, also a student of Dr. Kirk, makes a cogent forensic argument regarding the potential value of crime reconstruction to the court in terms of establishing what has actually happened in a given case:
Crime reconstruction, as argued, involves examining the available physical evidence, those materials left at or removed from the scene, victim, or offender. These materials are used by the forensic scientist establish to contact between the suspect and victim or scene
according to the principle proposed Dr. Locard. These forensically established contacts are then considered in light of available and reliable witness, victim, and offender statements. From this, theories regarding the circumstances of the crime can be generated and falsified by logically applying the information of the established facts of the case. Left standing, ideally, will be legitimate, logical conclusions regarding the actions surrounding the commission of the crime or as put by the fictional Sherlock Holmes in the Sign of Four, "when you have eliminated the impossible, whatever remains, however improbable, must be the truth."
The Assumption of
Even though a reliable chain of evidence may be established1, physical evidence may have been altered prior to or during its collection and examination. Unless the integrity of the evidence can be reliably established, and legitimate evidentiary influences accounted for, the documentation of a chain of evidence, by itself, does not provide acceptable ground upon which to build reliable forensic conclusions.
Consideration of evidentiary influences, or Evidence Dynamics, is a necessary part of the crime reconstruction process.
The general term Evidence Dynamics has been developed by the authors to refer to any influence that changes, relocates, obscures, or obliterates physical evidence, regardless of intent. Evidence Dynamics comes into play during the interval that begins as evidence is being transferred, and ends when the case is ultimately adjudicated. For those who are familiar with such evidentiary influences, and account for them in their analysis, this terminology is intended to provide a necessary and useful descriptor. An appreciation of Evidence Dynamics on what can be concluded from the physical evidence is requisite, and often pivotal, to the reconstruction process.
In the interpretation of Evidence Dynamics, two questions require attention. First, is there an item of evidence that has been demonstrably influenced between the time of the crime and the time of examination? If an item of evidence has been moved, changed, or obscured, then this must be factored into the examiner's analysis in terms of when and how. Second, is there evidence of a circumstance that could have obliterated or influenced evidence? Forensic scientists can only include in their analyses those things for which evidence exists. However, if there is no reasonable suggestion of circumstances that could have influenced or obliterated evidence, then the examiner should not assume that they occurred.
There are many possible influences on Evidence Dynamics that should be considered as evidence is examined. A brief list, not meant to be all-inclusive, is provided below.
Offender actions: The actions of an offender during the commission of their crime and the post-offense interval influence the nature and quality of evidence that is left behind.
These can include Precautionary Acts, Ritual or Fantasy, and Staging. Precautionary Acts involving physical evidence are behaviors committed by an offender before, during, or after an offense that are consciously intended to confuse, hamper, or defeat investigative or forensic efforts for the purposes of concealing their identity, their connection to the crime, or the crime itself . Staging of the crime scene is a specific type of precautionary act that is done to deflect suspicion away from the offender. Staging often involves the addition of, removal of, and manipulation of objects in the crime scene to change the apparent "motive" of the crime.  Ritual or Fantasy may also influence the offenders actions during a crime, and can include such things as postmortem mutilation, necrophilia, and purposeful arrangement of a body or items in a scene. 
Victim actions: The victims activities prior to a crime may result in artifacts that are mistaken for evidence. The actions of a victim during an attack and in the post-offense interval can influence the nature and quality of evidence that is left behind. This includes defensive actions, such as struggling, fighting, and running, which can relocate transfer evidence, causing secondary transfer. The victims actions may also include cleaning up a location or their person after an attack.
Secondary Transfer: Transfer evidence, as we have established, is produced by contact between persons and objects [2, 8]. Secondary transfer refers to an exchange of evidence between objects or persons that occurs subsequent to an original exchange, unassociated with the circumstances that produced the original exchange2.
Witnesses: The actions of witnesses in the post-offense interval can influence the nature and quality of evidence that is left behind. This includes actions taken to preserve victim dignity, as well as the deliberate theft of items from the scene upon discovery of an incapacitated or deceased victim.
Weather/ Climate: The weather or climate of a crime can influence the nature and quality of all manner of evidence that is left behind. This includes the destruction or obliteration of evidence by all manner of weather, as well as the effects of weather and climate on rates of body and biological transfer evidence decomposition.
Decomposition: Naturally occurring rates of decomposition, over time, can obscure, obliterate or mimic evidence of injury to a body. The clothing from a decomposed body will normally receive less attention for trace or transfer evidence.
Insect Activity: The actions of flies, ants, beetles, and other insects can obliterate the wounds on a body. They may also move, remove or destroy the transfer evidence.
Animal Predation: The feeding activities of all manner of indigenous wildlife from mice to coyotes and bears can relocate evidence, obliterate patterns, and further obscure, obliterate or mimic evidence of criminal injury to a body.
Fire: In cases were fire is involved, intentional or otherwise, the result can be the obscuring of all manner of physical evidence related to criminal activities, as well as its potential destruction. The evidence showing the actions of the offender regarding the primary offense are obscured if not eliminated by the subsequent arson. Evidence of the arson may remain.
Fire Suppression Efforts: In cases were fire is involved, there may be suppression efforts made. These efforts typically involve the use of high-pressure water, heavy hoses, perhaps chemicals, and firemen. Any of these, alone or in concert, can relocate the evidence, obliterate patterns, cause potentially misleading transfers, and/or add artifact-evidence3, to the scene.
Police: The duty of the first officer on the scene is to protect life, not to preserve evidence. They must establish that the scene is secure from further attacks. Their actions may relocate evidence, obliterate patterns, cause transfers, and add artifact-evidence to the scene.
Emergency Medical Technicians: The actions of emergency medical personnel engaged in life saving activities in a crime may relocate evidence, obliterate patterns, cause transfers, and add artifacts mistaken as evidence. As well, they can add therapeutic injuries to the victim.
Scene Technicians: The actions of technicians working in the physical evidence recognition, preservation, documentation, and collection phases in a crime scene are expected to remove evidence without obliterating patterns, causing potentially misleading transfers, and adding artifact-evidence to the scene. The technicians must thoroughly document the scene prior to entering so the changes that occur are obvious.
Forensic Scientists: The actions of forensic scientists will also remove evidence, obliterate patterns, may cause potentially misleading transfers, and add artifact-evidence to the scene. This can occur by virtue of improper storage or destructive analytical techniques, or the addition of transfer and/or pattern evidence to a victim's body or clothing during transport and/or storage.
Coroners: The actions of the coroner in removing the body from the scene can move evidence, obliterate patterns, cause potentially misleading transfer, and add artifact-evidence to the scene. This includes the physical removal of the body from the location where it was discovered, the placement of the body into a "body bag," and the process of transporting the body from the scene. These actions will change pattern evidence on the clothing of the victim and may destroy potential valuable transfer evidence.
Journal of Behavioral Profiling:
Volume 1, Number 1, January 2000
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