Crime scene investigation

DEFINITION: Process of recognizing, preserving, collecting, analyzing, and reconstructing evidence located at a crime scene

SIGNIFICANCE: By using proven principles and procedures to ensure that all physical evidence at a crime scene is discovered and analyzed, crime scene investigators help to clarify exactly what happened there. The information they gather can link possible suspects to the scene or eliminate them from suspicion.

“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.

Crime Scene Classification

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 of the larger crime scene, but each also constitutes an individual scene for processing. The methods and techniques employed by crime scene investigators depend on both the larger scene and the individual portions within it.

A microscopic crime scene is one in which trace evidence, residues, and similar evidence may be found. Microscopic scenes are often parts of larger macroscopic scenes and therefore require individual processing as well. In processing these scenes, investigators usually require the aid of mechanical or other tools for examination and analysis. A microscopic scene may also be a secondary or higher-level scene that is independent of the primary macroscopic scene. An example is hair or fiber samples from a victim that may be found in a suspect’s car. Such samples create a secondary scene that requires microscopic examination. Other examples of microscopic scenes include the clothing of a murder victim, the tire tread left by a getaway car, and the genetic material used in DNA (deoxyribonucleic acid) identification.

A third method of classifying crime scenes is based on the type of crime committed, as different kinds of evidence may be found at the scenes of homicides, robberies, sexual assaults, and other crimes. The methods for processing crime scenes are often determined by the types of crimes and the expected evidence. For example, the scene of a sexual assault is likely to involve evidence very different from the evidence found at the scene of a robbery.

The type of criminal behavior associated with particular crimes may also be used in classifying crime scenes. This is especially important when investigators are attempting to establish the perpetrator’s modus operandi, or method of operation (MO), and to recognize potential “signatures” of the perpetrator. The MO used by the perpetrator of a particular crime can often help to define potential suspects, and forensic investigators can help identify and analyze elements of the crime scene that point to the perpetrator’s MO.

Crime Scene Objectives

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 the crime scene investigator is to identify witnesses and secure sufficient statements from them. This task includes verifying witness statements, corroborating the statements with other evidence, and, in some instances, disproving the statements as related to physical evidence. The identification of witnesses often helps define other processes and objectives for the crime scene investigation.

The next objective is the identification of suspects. Often a culmination of the earlier objectives, the identification of suspects brings together physical evidence, witness statements, and evidentiary conclusions and allows the investigators to move to their final objective: reconstruction of the crime and the potential evidence related to it. Crime scene investigation focuses on the how and why of the criminal act. In crime scene reconstruction, investigators put together the pieces of evidence, including witness statements, to create a picture of the crime in question.

Methods of Crime Scene Investigation

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 collection and preservation methods must be used for particular evidence types, so that the evidence is best protected for later use. In some instances, evidence may be collected and preserved for archival purposes, whereas in others it may be secured for later analysis. Investigators must follow a specific set of procedures for processing each type of evidence.

The final step of linear progression is known as individualization. This involves the evaluation of evidence and interpretation of the findings as related to the crime. For example, although many fingerprints may be found at a given crime scene, only select prints will be usable for helping to determine the suspect. The individualization of each set of prints allows investigators to identify persons on the scene, which in turn helps to build a better understanding of the crime itself.

The second process in crime scene investigation is known as nonlinear progression. This process focuses on patterns of recognition and reasonable inference. Also known as a dynamic process, in this step investigators search for patterns and links between evidence and the elements of the crime. This step focuses on critical scene analysis and specified definition techniques. During this process, which is less systematic than linear progression, investigators use inferences and logic to draw connections that lead to reasonable conclusions.

Processing the Crime Scene

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 to evaluate the scene and make recommendations concerning additional investigative needs. A crime scene technician may be called to the scene to process physical evidence, but in smaller departments this task may actually fall on the responding officer.

and Crime Scene Investigation

The tools, methods, and techniques used in modern crime scene investigation have made tremendous advances since the middle of the twentieth century. 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 the application of scientific methods to criminal investigations has changed very quickly. Forensic science has seen great improvements in technologies that enable the identification of trace or microscopic evidence, and crime scene investigators in the field have increasing access to devices that were once reserved for the laboratory. Major developments in forensic science technology in the twenty-first century include automated systems that can perform DNA and fingerprint analyses; artificial intelligence-powered facial recognition, and virtual reality crime scene reconstruction.

Bibliography

Adams, Thomas F., Alan G. Caddell, and Jeffrey L. Krutsinger. Crime Scene Investigation. 2nd ed. Prentice, 2004.

Bennett, Wayne W., and Kären M. Hess. Criminal Investigation. 10th ed. Delmar Cengage, 2013.

Fisher, Barry A. J. Techniques of Crime Scene Investigation. 8th ed. CRC, 2012.

Gilbert, James N. Criminal Investigation. 8th ed. Pearson, 2012.

Lowden, Olivia. "The Technology Trends Shaping the Future of Forensics." BCC Research, 18 July 2023, blog.bccresearch.com/technology-trends-shaping-the-future-of-forensics-industry. Accessed 12 Nov. 2024.

Makin, David Alan. DNA and Property Crime Scene Investigation. Elsevier, 2015.

Maloney, Michael S., Donald Housman, and Ross M. Gardner. Crime Scene Investigation Procedural Guide. CRC, 2014.

Ogle, Robert R., Jr. Crime Scene Investigation and Reconstruction. 4th ed., Pearson, 2017.