Crime Scene Investigation
Crime scene investigation (Forensic Science)
“Crime scene investigation” is an umbrella term often used to refer to a range of methods and techniques applied during a criminal investigation. Focused on the discovery, recovery, and processing of evidence, crime scene investigation applies reasoned principles in the pursuit of truth. From the moment a crime is discovered until the final appeal in court, the methods and techniques employed during crime scene investigation are under scrutiny.
Modern crime scene investigators combine the logic of fictional detective Sherlock Holmes with advanced scientific techniques in identifying and processing evidence. The basic crime scene procedures used by forensic scientists focus on physical evidence recognition, documentation, collection, packaging, preservation, and analysis. A systematic approach to the investigative task reduces the likelihood of error and improves the investigators’ chances of attaining the ultimate goal of justice.
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Crime Scene Classification (Forensic Science)
Crime scenes are traditionally classified based on location, complexity, and relation to the crime in question. The first step in classifying a crime scene is to define the outer boundaries of the physical location. These boundaries establish the geographic limits within which the initial crime will be investigated; this area is known as the primary scene.
The nature of some crimes may involve more than one physical scene, and these are often identified as the secondary, tertiary, and subsequent scenes. For example, in a murder case the death may occur in one location and the body of the victim may be found in another. The primary scene is where the killing took place; the secondary scene is the location where the body was discovered. Both scenes may reveal relevant evidence, and the processing of both constitutes an important part of the criminal investigation.
Crime scenes are also classified as macroscopic or microscopic. A macroscopic crime scene is one that can be viewed and analyzed with the naked eye. Such a scene also includes the potential for several levels of the investigation. Each macroscopic scene is a part of the larger crime. For instance, the scene of a robbery at a convenience store may involve the doorway where the culprit entered, the cash register from which money was stolen, and the back room of the store where the offender placed the clerk before leaving. Each of these scenes is a part...
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Crime Scene Objectives (Forensic Science)
Each crime scene requires a specific systematic investigative approach that is adapted to the needs of that particular crime or scene. The objectives of any crime scene investigation are to identify, preserve, collect, and interpret each piece of evidence. In processing a scene and analyzing evidence, crime scene investigators typically follow a pattern aimed at meeting specific objectives.
The first objective is to determine the essential facts of the case as they relate to the establishment of a crime and its corpus delicti (Latin for “body of the crime”—commonly defined as the substantive nature of the crime). The corpus delicti makes up the essence of a crime, including the legal elements and proof arising from evidence. By first defining the essential facts, investigators can best determine the types of evidence likely to be found and the appropriate processes for recovery of that evidence.
The second objective of the crime scene investigator is to determine the perpetrator’s MO. Each crime type requires that the perpetrator perform specific actions to achieve the criminal goal, but perpetrators use many different means for achieving their goals. Individual perpetrators may have specific methods they tend to use in carrying out given crimes. By establishing the MO, investigators can help to define the type of evidence as well as its application to the criminal conduct.
The third objective of...
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Methods of Crime Scene Investigation (Forensic Science)
Crime scene investigation often involves two distinct processes. The first, known as linear progression, focuses on the systematic identification of evidence. Often performed by technicians, this process follows specific guidelines and patterns for identification and management of evidence. In this process, proper procedure is crucial to guarantee the high quality of the evidence and thus support an effective investigation.
Linear progression focuses first on a system of recognition. Initial steps in this part of the crime scene investigation include scene survey and documentation. The investigators describe the crime scene in narrative reports that are often supplemented by diagrams, sketches, photographs, and related material.
The next step in linear progression is identification, which may include comparison and testing. In this step, the investigators identify potential evidence to separate it from irrelevant items found at the crime scene and to help in the collection, preservation, and processing of the evidence. For example, fingerprints discovered in the initial phase of identification of evidence may be lifted at the scene and later identified through a logical system of comparison. The testing of evidence may include chemical, biological, physical, and other methods.
Together, the collection and preservation of evidence constitute an important step in linear progression. Specific...
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Processing the Crime Scene (Forensic Science)
The first step in processing a crime scene is to secure it. This begins when the first responding officer arrives at the scene. Initial concerns are for the safety of any victims, witnesses, and others who may be on the scene, but as soon as the responding officer is sure that no persons are in danger, the focus turns to the protection of potential evidence. In many instances, responding officers work to address these two concerns simultaneously.
Securing the crime scene allows investigators to control the potential for loss or destruction of evidence. It also provides an opportunity for investigators to begin the chain of custody—that is, the documentation of the location of all the evidence recovered during the investigation and its eventual use in the courts.
In large police departments, and especially on major crime scenes, the tasks associated with crime scene investigation may be assigned to different individuals. In some instances a lead investigator takes a proactive and supervisory role, controlling and monitoring all activities at the crime scene. In other agencies, a crime scene supervisor takes that role; in still others, various crime scene duties are assumed by individual units.
Small crime scenes and relatively low-level crimes may involve limited numbers of investigators. For example, a classic case of burglary may initially involve only the responding officer, who then has the duty...
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Forensic Science and Crime Scene Investigation (Forensic Science)
The tools, methods, and techniques used in modern crime scene investigation have made tremendous advances in the past fifty years. The role of forensic science in law-enforcement investigations has increased steadily as methods have improved. Scientific testing that was once prohibitively expensive is now readily available, and new technologies have increasingly improved the accuracy of the findings of criminal investigations.
These advances have come at some cost, however. For instance, jurors in general may have high expectations regarding what investigators can do at crime scenes, in part because of the fictional portrayals of forensic investigators that have become common on television and in films. This means that investigators must be particularly careful to follow standard operating procedures as well as the accepted techniques related to individual kinds of crimes.
Crime scene investigation has also changed dramatically because of changes in the investigative approach taken by many law-enforcement agencies. The trend toward community-oriented policing, among other developments, has led to more accommodating approaches to interagency investigation. The nature of criminal activity, especially when similar crimes take place across multiple jurisdictions, demands that agencies cooperate with each other in the investigation process.
The foundations of science change slowly, but...
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Further Reading (Forensic Science)
Adams, Thomas F., Alan G. Caddell, and Jeffrey L. Krutsinger. Crime Scene Investigation. 2d ed. Upper Saddle River, N.J.: Prentice Hall, 2004. Handbook for law-enforcement professionals focuses on excellence in the conduct of crime scene procedures.
Bennett, Wayne W., and Kären M. Hess. Criminal Investigation. 8th ed. Belmont, Calif.: Wadsworth/Thomson Learning, 2007. Provides in-depth discussion of forensic techniques and procedures.
Fisher, Barry A. J. Techniques of Crime Scene Investigation. 7th ed. Boca Raton, Fla.: CRC Press, 2004. Provides a broad overview of many areas of forensics, including the specific methods used by investigators at crime scenes.
Gilbert, James N. Criminal Investigation. 6th ed. Upper Saddle River, N.J.: Pearson Prentice Hall, 2004. Comprehensive text includes discussion of the procedures forensic scientists follow at crime scenes.
Ogle, Robert R., Jr. Crime Scene Investigation and Reconstruction. 2d ed. Upper Saddle River, N.J.: Prentice Hall, 2007. Well-organized text covers all aspects of the work of forensic scientists during criminal investigations.
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Crime Scene Investigation (World of Forensic Science)
Scene processing is the term applied to the series of steps taken to investigate a crime scene. Although the methods and techniques may differ between the experts involved, their goals are the same: to reconstruct the exact circumstances of the crime through the identification of the sequence of events and to gather physical evidence that can lead to the identification of the perpetrators.
Crime investigation usually begins at the place where the crime was committed. The area must be isolated and secured to prevent the destruction of crucial physical evidence that can lead police to link the perpetrators to the victim. The size of the area to be isolated and secured varies with each case, and a series of protocols designed to secure and protect evidence are followed.
The first police officer on the scene is responsible for preventing other non-essential police personnel and civilians from entering the scene and often establishes a perimeter around the crime scene with ropes or tapes. If witnesses are present, they are identified and remain outside the perimeters of the crime scene while waiting for questioning by the investigation team. If a death has occurred, a coroner, a crime scene technician, and investigators are requested to the scene to assist the police.
The crime scene technician is an expert in finding and identifying physical evidence such as hairs, fibers, empty bullet capsules, bloodstained objects, and body fluids which may be found in carpets, on furniture, on walls, etc. The scene and each piece of evidence is carefully photographed and then properly collected and conditioned to avoid contamination, to be later analyzed at the crime laboratory. This expert also writes a thorough report of the scene and describes the evidence found.
The investigator interviews witnesses, gathers information from the police on the scene, the crime scene technician, the coroner, pathologist, and other specialists that are present (such as a forensic anthropologist). The investigator is also responsible for the management of information given to the press, deciding what should or should not be initially disclosed to the public in order to not endanger the success of the investigation. The investigator will discuss with the prosecutor's office the available evidence and other information to determine the legal direction of the investigation, since both are responsible for the entire investigative process and for building a case when prosecuting persons charged with the crime.
The coroner or medical examiner on the scene instructs the pathologist as to what physical evidence
For investigative purposes, the area of a crime scene is always larger than the actual site or room where the crime occurred. Therefore, the first officer on the scene must be trained to identify and isolate the primary and secondary areas of the scene. If a body was found indoors, for example, the crime scene primary area is the room where it was found. The secondary crime scene perimeter is the remainder of the house or building, along with all the doors, windows, and corridors that give access to the primary area, including front and back yards. The secondary areas may contain important evidence of a fight, footwear prints, fingerprints, broken windows or doors, tire prints, or bloodstains.
In cases when a highly probable suspect is known, the suspect's house or car may also be treated as a secondary crime scene area, even when it is not located in the proximity of where the crime was committed. All physical evidence identified in both areas may help in the reconstruction of the chain of events of the criminal act.
The services of a forensic anthropologist are requested when highly decomposed or charred human remains are found, when difficulty in gathering physical evidence is experienced, or when the identification of the victim or the cause of death is not apparent. A series of physical changes and interactions with soil bacteria, insects, and animals takes place when humans are buried, especially in mass graves. In these cases, the anthropological analysis of hair, bones and soft tissues (if available) may reveal race, gender, stature, approximate age at the time of death and, often, the cause of death. The conduction of evidence gathering in these cases is a different procedure, usually not familiar to most crime scene technicians, and involves archeological techniques, soil analysis, identification of buried debris, recognition of buried marks of hands or footwear, and animal evidence.
Forensic anthropologists are often consulted for "cold case" investigations when human remains are unexpectedly found. These scenes should also begin with securing of the scene by the police, in case a determination is later made that a crime was committed. At least 10 yards around the spot where the remains are (or are believed to be buried) should be isolated. The anthropological gathering of evidence will take at least a full day, and when the remains are buried, two days. Only after this phase is completed can the remains be removed from the site. Forensic anthropology techniques may supply not only relevant physical evidence but also contextual information about the circumstances of the death, through the three-dimensional mapping and analysis of the scene, the location and interrelationship of physical evidence scattered around the remains, depth of the grave or pit, and geological characteristics of the soil.
SEE ALSO Analytical instrumentation; Animal evidence; Anthropology; Anthropometry; Artificial fibers; Autopsy; Ballistic fingerprints; Bloodstain evidence; Bite analysis; Crime scene reconstruction; CODIS: Combined DNA Index System; Death, cause of; Decomposition; DNA fingerprint; Entomology; Exhumation; Fingerprint; Hair analysis; Impression evidence; Pathology; Trace evidence.