Crime Scene Investigation

It would not be an exaggeration to assert that crime scene investigation ranks with the most intellectually challenging and difficult of human activities. It is also one of the most misunderstood. In practice, crime scene investigation is rarely carried out efficiently and effectively. Successful outcomes, when and where they occur, are often fortuitous rather than following from intelligently adaptive plans or designs.

There seems to be an inexplicable disconnect in the public's perceptions of the problem of crime scene investigation. In fictional portrayals dating from the Sherlock Holmes stories of Sir Arthur Conan Doyle to the present, the interpretation of physical clues at a crime scene is seen as the epitome of intellectual prowess. Judging from the allocation of expertise and [Page 112]resources, this is a far cry from the importance accorded this activity in the real world today.

From a philosophical or theoretical viewpoint, the crime scene can be viewed as a recording device and a recording medium. To some degree, the scene provides a continuous and continuing record of events that transpire at the particular location. Events, including those that ultimately may be defined as crimes, involve human-initiated interactions that alter the environment as well as items within it in myriad ways. The alterations may be subtle or profound. It is the creation of these alterations that results in the production of the record. The interactions produce the alterations, and thus the record, according to physical laws. The resulting alterations to the scene and to some subset of the items within it form the physical evidence record. The record is, by its nature, incomplete and, to some extent, transitory. Postevent interactions can complicate the physical evidence record or even overwrite it. It is important to attempt to freeze the record soon after the event of interest, but this is not always possible. Although the concept of a pristine crime scene is a myth, it is important for investigators to act promptly to attempt to preserve the record that remains at the time that law enforcement personnel take control over the scene.

Because the interactions among items and surfaces at the crime scene follow physical laws in producing the physical evidence record, this makes the analysis of the scene itself a scientific problem—a point that is not widely appreciated. Certainly, it has long been recognized that individual items of physical evidence removed from crime scenes require a scientific analysis, but with notable exceptions, this realization has not been extended to crime scenes themselves. In most law enforcement jurisdictions in the United States, scientific expertise is absent from the initial crime scene investigation. This is true for many other parts of the world as well, and it is a situation that needs to be rectified. An argument can be made that scene investigations should be carried out exclusively by forensic scientists, but at the very least, experienced forensic scientists should form part of the crime scene investigation team.

The physical evidence record is produced in varying degrees of detail, but it is axiomatic that it is incomplete, and furthermore, that it is likely to be degraded to some degree following the event. A pristine crime scene is an unrealizable ideal. As noted earlier, it does not exist in the real world. Even in the most favorable circumstances, postevent factors will unavoidably alter the record left by the interactions taking place during the event of interest. The mere discovery of an event, and the steps leading to a conclusion that a crime has taken place and that the scene is worthy of attention, may destroy evidence. This is a reality that must be faced. If there is the possibility of saving the life of an injured person at the scene, the steps necessary to aid the victim take precedence over those directed at documenting and preserving physical evidence. The difficulties increase exponentially with large-scale events involving the injury and death of many people. Of course, this realization is not justification for a cavalier attitude toward scenes and physical evidence.

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