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Crime scenes contain the forensic evidence required to apprehend criminals. The proper collection and processing of physical evidence is of primary importance to most police investigations. Evidence can not only establish the fact of the offense and identify the perpetrator, it may even lead to a conviction. In collecting this evidence we must be conscious of the public's Fourth Amendment rights and not violate them in this collection of evidence. Unfortunately, poorly conducted crime scene investigations can sometimes either destroy evidence or render it useless.
Law Enforcement should approach the crime scene investigation as if it will be their only opportunity to preserve and recover these physical clues. They should consider other case information or statements from witnesses or suspects carefully in their objective assessment of the scene. Investigations may change course a number of times during such an inquiry and physical clues, initially thought irrelevant, may become crucial to a successful resolution of the case.
The primary responsibilities of the initial responder to a crime include the following: (1) to preserve life; and (2) to control suspects and witnesses. Once these two objectives have been achieved, the initial responder should focus their attention on protecting the crime scene. The initial response to an incident shall be expeditious and methodical. Upon arrival, the officer(s) shall assess the scene and treat the incident as a crime scene. The initial responder should note or log dispatch information such as names, address, time, type of call, and any other relevant information. Be aware of any persons or vehicles leaving the crime scene. The importance of preserving the scene and its adjacent areas in their original condition cannot be overemphasized. Approach the scene cautiously, scan the entire area to thoroughly assess the scene, and note any possible secondary crime scenes. Be aware of any persons and vehicles in the vicinity that may be related to the crime. Remain alert and attentive; Assume the crime is ongoing until determined to be otherwise. also treat the location as a crime scene until assessed and determined to be otherwise.
It is usually the uniformed peace officer who first arrives at the scene of a crime. After controlling any dangerous situations or persons, the initial responding officers' next responsibility is to ensure that medical attention is provided to injured persons while minimizing contamination of the scene. The initial responding officer shall ensure that medical attention is provided with minimal contamination of the scene by guiding medical personnel to the victim to minimize contamination or alteration of the crime scene. Point out potential physical evidence to medical personnel, instruct them to minimize contact with such evidence (e.g., ensure that medical personnel preserve all clothing and personal effects without cutting through bullet holes, knife tears), and document movement of persons or items by medical personnel. Instruct medical personnel not to clean up the scene and to avoid removal or alteration of items originating from the scene.
Protecting the evidence typically involves the establishing a perimeter. In fact, for some crime scenes, two perimeters may be appropriate (Garrison, 1994, pp. 18-20). Only the investigator in charge and those personnel that he gives permission to should be allowed to cross these boundaries (Dienstein, 1962, pp. 16-26).
Detectives and supervisors are normally in charge of investigations. There should, however, only be one person in charge of the crime scene itself. The first question that the investigator will ask when he arrives is as follows: "Has anyone been allowed to enter the scene?" (Dienstein, 1962, pp. 16-26)? The investigator should then use whatever resources are available (e.g., barricades or other uniformed officers) to further protect the area. Such measures exclude both curious bystanders and curious officials. Investigators often must turn away any number of officials--both in and out of uniform--who could unintentionally destroy evidence.
Once the area has been secured, the investigator then carries out the duties of search commander. Initially, the commander must obtain the following information: "The time of the arrival of the first officer at the scene, who was present, what was said, and whether or not everything is exactly as it was when the officer arrived" (Dienstein, 1962, pp. 16-26). Then, the addresses of all persons found on or adjacent to the scene should be collected. Although these people are questioned about their exact location at the time of the crime, they do not usually undergo interrogation on the spot. Rather, such persons are simply removed from the scene and separated: They should not be allowed to talk to each other until each has been carefully questioned and statements have been obtained individuals considered as suspect(s) should be read their Miranda Rights. Any violation of Fourth Amendment rights could jeopardize any evidence obtained during an interrogation or interview for use in the case at a trial.
The next phase of crime scene investigation consists of surveying the scene. Defining and controlling boundaries provide a means for protecting and securing the crime scene(s). The number of crime scenes and their boundaries are determined by their location(s) and the type of crime. Boundaries shall be established beyond the initial scope of the crime scene(s) with the understanding that the boundaries can be reduced in size if necessary but cannot be as easily expanded. The investigator needs to get an "over-all picture of the area in which the offense occurred" (Dienstein, 1962, pp. 16-26). After a preliminary survey has been performed, the crime scene examination should be initiated. The investigator must try to start the investigation "cold" (Dienstein, 1962, pp. 16-26). There should be no preconceived notions of what happened, how it happened, or who might have done it. Such conclusions must be based solely on the evidence found at the scene.
It is during this initial stage of the investigation, that the search commander has the scene photographed and sketched. Photography provides investigators with an accurate and permanent record. Nothing at a crime scene should ever be touched, picked up, or moved until it has been photographed. Only a "true" photograph can be presented in court (Dienstein, 1962, pp. 16-26). If it can be shown that something in the picture was tampered with, or that there are objects present that were not there originally, then the photograph cannot be used as evidence. Photographers should be present throughout the investigation. In addition to photographs, the search commander also has a sketch made of the area. Sketching should be started as soon as possible. These freehand drawings are typically oriented by compass directions. Moreover, the location of all sketched objects should be determined by accurate measurements. While photographs reproduce everything within the range and field of the camera lens, sketches include only certain essential items. There are three types of crime scene photographs and sketches. These include the following: (1) those that describe the locality; (2) those that reproduce the immediate grounds; and (3) those that cover the details of the scene. Locality reproduction produces a picture of the crime scene and its surroundings. These pictures should include such things as neighboring buildings, streets, and sidewalks. Second, reproductions of the grounds should describe the crime scene's immediate surroundings (e.g., the house, the garden, etc.). Finally, a details picture shows only the scene itself (e.g., the room in which the offense was committed).
During photography and sketching, the search commander must formulate a plan of action. This involves designating the various crime scene areas and objects that need to be searched and inspected. The commander must also decide how many investigators to assign to the case. Once the search has begun, it is up to the searchers to decide what objects will be dusted for latent prints and what objects will be removed as evidence. Searches need to be both thorough and accurate: Nothing should be taken for granted. Furthermore, searchers should not attempt to rely on their memories. Instead, everything "of possible significance" must be recorded (Dienstein, 1962, pp. 16-26).
With the development of more advanced laboratory technologies, the role of physical evidence in the apprehension and prosecution of criminals has expanded considerably. It is generally assumed that by gathering more evidence, the investigator increases the likelihood of identifying the suspects (Greenwood et al., 1977, pp. 165-166). Evidence is defined as "anything that may be presented in determining the truth about a fact in question" (Dienstein, 1962, pp. 16-26). Physical evidence has three general purposes: (1) it can verify that a crime has been committed; (2) it can identify the person or persons who committed the crime; and (3) it can exonerate all other persons who may be under suspicion. Physical evidence proving that a crime has been committed may include such things as broken door locks or bodily injury to the complainant. Evidence indicating that the suspect was at the scene of the crime can consist of fibers or injury to the suspect (Greenwood et al., 1977, pp. 143-149). These forms of evidence support probable cause in having a warrant issued for further investigations that lead away from the actual crime scene. There are two main types of evidence found at crime scenes: (1) fixed evidence; and (2) movable evidence. Fixed evidence includes such things as latent fingerprints, shoe prints, tire prints, tool marks, and objects which cannot be removed because of bulk, weight, or other factors. In contrast, movable evidence consists of items which can be easily removed and stored. Finally, it should also be noted that almost anything can constitute a clue in a criminal investigation. Therefore, everything must be recorded and nothing should be overlooked.
Once evidence is discovered, the search commander should have its location reproduced by sketch and/or photograph. The commander then marks the evidence for purposes of identification. The searcher who discovered the evidence should stand by as a witness to this marking and handling procedure. The term, "chain of custody," refers to the "possession of evidence" (Dienstein, 1962, pp. 16-26). Investigators must be able to establish the continuous possession of evidence from the moment that it is discovered until the time that it is presented in court. By having the search commander handle all evidence, this chain of custody is reduced.
In recent years, many police departments have augmented their evidence gathering capabilities by hiring additional personnel. Evidence technicians, or Crime Scene Search Officers, are highly trained crime scene processing specialists (Greenwood et al., 1977, pp. 143-149). These personnel can be dispatched just like patrol officers. Evidence technicians are generally used whenever there is retrievable physical evidence, or whenever the patrol officer feels that a photograph of the crime scene could be of benefit (Greenwood et al., 1977, pp. 143-149).
A coroner may also be present at a crime scene. Coroners serve as a "middle man between the medical examiner and law enforcement" (Voelker, 1995, p. 1164). A coroner with forensic training may also act as a liaison between law enforcement, the media, and the public.
The presence of many diverse personnel at a crime scene can give rise to conflict. However, everyone present has a specific job to do; moreover, each individual task is an important part of the entire mission. Search commanders should direct all activities such that conflict is minimized. As Dienstein (1962) emphasizes, "Teamwork is essential to crime scene search" (Dienstein, 1962, pp. 16-26).
Besides hiring personnel, many departments are also in the process of updating their criminalist equipment. For example, Anchorage Alaska's police department recently converted a customized motor home into a modern crime scene vehicle. By making crime scene investigation faster and more thorough, such tools can improve a team's overall efficiency.
There are various problems that may be encountered during crime scene investigations. Two of these include staging and contamination. Staging involves the alteration of a crime scene prior to the arrival of police. There are different reasons for staging. For one, an offender might try to direct investigators' attention elsewhere. Such persons may act overly cooperative or appear extremely distraught. Second, staging can also represent an attempt to protect either the victim or the victim's family. Such cases usually involve people who are concerned about the position, dress, or condition of a victim's body (Douglas & Munn, 1992, pp. 1-10).
Perhaps the biggest problem that crime scene technicians face, however, is crime scene contamination. Sensitive forensic techniques may be adversely affected by crime scene trampling. Police departments should have a written policy regarding crime scene protection and preservation. In addition, supervisors and investigators must set an example for the entire crime scene team by adhering to the guidelines.
Crime scene investigation is a complex process. It involves a number of different professionals and various areas of expertise. Only by acting as a team, however, will the members of such a diverse group ensure that their efforts result in a reasonable outcome. The alteration of a crime scene can cause investigators to draw erroneous conclusions. By expeditiously carrying out his responsibilities, the initial responder may determine the ultimate outcome of an entire investigation.