|Crime Scene Reconstruction|
Introduction to Crime Scene Reconstruction
Crime Scene Reconstruction- The use of scientific
methods, physical evidence, deductive reasoning and their
interrelationships to gain explicit knowledge of the series of events that
surround the commission of a crime.
While both of these activities may appear to be similar and are in fact related, it is important to note that they are not the same. The difference between the two is most easily understood by looking at which questions about the crime they attempt to answer. Crime Scene Reconstruction looks at the physical evidence and attempts to determine "What happened?" and "How did it happen?". Criminal Profiling looks at the physical evidence and the reconstruction and attempts to determine "Why may this have happened?" and "What does that tell us about Who may have done it?". It is important to keep in mind that only those directly involved in the crime know for sure what happened and why, and they may be unable or unwilling to say.
Why is it important to reconstruct the crime prior to profiling the offender? The answer is simple; until you know what happened, and how it happened (at least as much as possible), you have no basis for attempting to determine why and who.
This paper is intended as an overview of the types of reconstruction which may be possible and is not all inclusive (the number and types of things that may be reconstructed is like types of physical evidence- nearly limitless). For more specific information check the references or contact an expert in the field in question.
Types of Reconstruction
(Lee, pp. 192-3, lists 5 categories of reconstruction; one deals only with the amount of reconstruction done, and another lists several activities including criminal profiling which are not truly reconstruction).
In any given scene it may be possible to do a total or only partial reconstruction, and the reconstruction may use more than one technique (i.e. both trajectory and blood stain pattern reconstruction to locate the position of the victim). Some scenes lend themselves to reconstruction better than others. Traffic accidents are common scenes to reconstruct and often can be thoroughly reconstructed. Vehicles are rather massive objects that obey the laws of motion and often leave a wealth of physical evidence behind before, during and after an accident. It may be possible to show the entire sequence of events from the time the vehicles first enter the area of the accident until they come to rest following the accident.
Scenes involving the movement of people are more difficult. While it may be possible to say where a person was in the scene at several points in time, the manner in which they moved in the scene cannot be reconstructed. People may move slowly, quickly, hesitantly, jump up and down, run, skip, fall down, etc. all without leaving any particular trace behind. That said, there are of course the odd cases where the amount and type of physical evidence does allow the paths of the participants to be tracked with some accuracy; however, the vagaries of facial expression, gestures, and body language are simply impossible to reconstruct at all.
Below are some examples of the types of information which reconstruction may provide, again, this is not an all inclusive list. Some items also appear in more than one category, and it may be possible to use information from several areas to complete or validate the final reconstruction.
Examples of Types of Reconstruction:
Information Needed for Reconstruction
Generally speaking it is best to go to the scene, preferably at the time of the incident. Information may come from physical evidence, witness statements, and the reports of other experts. The reconstructionist should examine all scene photographs, autopsy protocol and photographs, measurements, drawings, notes, reports and items of evidence. Complete and accurate documentation of the scene is essential. Depending on the type of reconstruction being done this may include some different things such as the height and vertical/horizontal angles of shots into a wall, or the length and width of a bloodstain.
Steps in Reconstruction
Step 1, recognition of evidence, is arguably the most important, as Lee points out "Unless the potential evidence can be recognized, no further reconstruction can be carried out."
Steps 1-3, recognition, documentation and collection of evidence, are the heart of any successful scene investigation, and form the basis for the reconstruction.
Step 4, evaluation of evidence, examines the evidence (possibly following laboratory analysis) and looks at what information the evidence provides, and how reliable it is. At this time any witness statements should be compared to the evidence to see which parts of the statements can be supported or refuted by the evidence.
Step 5, hypothesis, is the formulation of an idea of how the event(or portions of it) occurred. This is not merely conjecture and should be firmly supported by the evidence.
Step 6, testing, looks to see how the hypothesis developed in 5 can be validated. This is accomplished by checking the evidence against known physical laws or devising a test to attempt to replicate the event(or the relevant segment).
Step 7, reconstruction, is the reporting of the results of the analysis. The results are reported as a range, where the event(or portions of it):
Application to Profiling
The reconstruction forms the foundation from which the profiler can begin. The reconstruction provides answers about what happened and how it happened. From there the profiler can begin asking "Why?" questions. Questions of "Why?" are not answered by the reconstruction. Neither are questions of Intent and Motive. Attempts to answer these questions may be investigatively useful, but lack the firm support of evidence required of reconstruction. Authors on both reconstruction and profiling speak of mentally re-enacting the events of the crime; again, this can be investigatively useful, but is not reconstruction.
As profiling is intended as an investigative tool, it attempts to go beyond the reconstruction, and answer questions of intent and motivation. From these admittedly subjective answers it can provide a clearer picture of the offender.
As an example, take a scene where the reconstruction shows as Event 1- "Subject breaks into residence through rear window. Window lock was previously secured and was jimmied with a thin, wide, black metal pry bar." Based on this information the profiler can begin to look at "Why?". Why did the offender choose this window? Why did he use this method of entry? Has it worked for him in the past? Where did he get the pry bar? Did he bring it with him or acquire it at the scene? The profiler can continue in this fashion through the scene, looking at the known facts, and then attempting to address the motivations behind the known actions. Working through the scene in this manner will also serve to highlight both the Modus Operandi and Signature aspects of the crime.
The reconstruction may show a sequence of events or actions that are unnecessary in the commission of the crime. In serial cases the recurrence of the same sequence at multiple scenes, or the modification of parts of it, may also assist in this determination.
A Case Study: The Murder of Donna Lynn Vetter
Donna Lynn Vetter was a 22-year old, white female. She worked as a stenographer for the FBI field office in San Antonio, Texas. On September 4, 1986, she was raped and murdered in her apartment. Ms. Vetter was last seen alive at 9:10PM, by a neighbor. She was found dead at 10:35PM; this places the occurrence of the offense to within a period of just over one hour. During this time the following events took place:
In this case the victim's continuing resistance led to an escalation of violence and ultimately to her death. When combined with the victimology and geoforensic information, the reconstruction allowed a thorough profile of the offender to be completed. 41,42
Conclusion: The Importance of Competent Crime Scene Work in Reconstruction and Profiling
Unless the analyst (reconstructionist or profiler) is one of the scene investigators, the basic scene work will likely already be completed, and any deficiencies will probably be impossible to correct. This may limit the information which the analyst can provide. To this end the need for continuing/advanced training for scene investigators cannot be overstated. While much of the evidence used for reconstruction speaks for itself and can be documented and collected using standard crime scene procedures, some types of reconstruction require specialized information.
The main three types would be Blood Stain Pattern, Traffic Accident, and Trajectory Reconstruction. All three types require specialized knowledge of what evidence to look for at the scene, and what documentation (photographs, measurements, etc.) are required to utilize the evidence in reconstruction.
An investigator at a traffic accident must know the difference between skid and yaw marks, for example. He must be able to document that the mark is a yaw rather than a skid, and know that each mark must be measured differently. Measurement of the length of a yaw mark is not much use in reconstruction.
Similarly a photograph of a bullet hole does not allow for trajectory reconstruction. We must know the position, height and angle at least, and knowledge of the direction is helpful.
A great deal of specialized knowledge is required for the proper interpretation of blood stain patterns. Without this knowledge the investigator may not even know what he needs to document, let alone how to do it.
Without competent, thorough scene work, the subsequent analysis may be incomplete or impossible.
1. Bevel, T., "Crime Scene Reconstruction," Journal of
Forensic Identification, 41(4), 1991, pp. 248-54.
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