Ways to collect physical evidence

Ways to collect physical evidence


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Criminal Justice:


Ways to collect physical evidence


In Criminal Justice, the collection of physical evidence is very important in determining the outcome of a case. When good evidence is collected, justice is achieved in the courtroom, and the innocence of a suspect is proven. Physical evidence refers to the tangible evidence that is found in a crime scene. This paper looks critically at what it entails to collect physical evidence.

Types of physical evidence found at crime scenes

Biological evidence is among the evidence found on a crime scene. Examples of the biological evidence are DNA, blood, sperm and even vomit, which originate from living beings. The Locard’s Exchange principle ascertains that physical evidence is to be found at a crime scene. This is because a perpetrator of crime always leaves or takes something from the scene of the crime. Tiny pieces of evidences are referred to as trace evidences these include evidences such as textile fibers, which are tiny and cannot be visible to the naked eye. These would require vacuuming the suspect surface (Bergman, 2009).

Apart from trace evidence, we also have the impression evidence, which are found from impressions made by a perpetrator. One such evidence includes the shoe prints left at a crime scene. It should be noted that tire tracks and shoe prints fall into the genre of class evidence and thus they cannot convict a felon in a criminal court. Even with this in mind, they assist exceedingly in conducting investigation and leading to individualizing evidence.

Methods and ways to collect physical evidence

Physical evidence is a very crucial aspect of crime investigation and ultimately in prosecuting a suspect in a court of law. Therefore, a lot of caution should be taken when dealing with physical evidence. Evidence must therefore be collected and analyzed properly. Emphasis is laid on every crime, and the investigator must trend with a lot of caution at the scene of crime to avoid contamination. Packaging methods vary according to the nature of evidence while, on the other hand, for physical evidence to be admissible in a court of law the chain of custody has to have no flows (Turvey B 2008).

How they are collected, how they are packaged, and how they are preserved

There are many ways of collecting physical evidence. This is done by looking at marks on the clothing, bruises cuts or marks on the body, defense wounds and even injuries on bodies. Missing items, blood and other bodily fluids and including other foreign objects that look out of place also count as physical evidence. In collecting physical evidence from the crime scene, there are a number of patterns from which to choose. These include inward spiral, where the criminal justice investigator starts from the outside and works towards the centre. The next is the outward spiral where the investigator starts from the inside towards the outside. The other one is the parallel, which reacquires a-team to move from one end to the other in straight lines. We also have the grid, which has two spirals crossing each other. The other being the zone search which divides the scene into parts for individual evidence collection. Examples of these are footwear, glass and controlled substances and drugs.


This evidence is collected by photographing the impression on the surface. Thus, the quality of the photograph taken is extremely crucial. After the photographs are taken, a case report is drawn, which is not placed together with the evidence envelopes where the photographs are put. A chain of custody is then established. The evidence is then placed in a container, which is marked with the case number, item and a brief description. The seal is then personalized by a signature of the person sealing the container and date. The physical evidence is then sent to the laboratory, and after being analyzed, it is stored in the police evidence room.


These are found on crime scenes where windows are broken in burglary, headlights, in hit-and-run cases or bottles used as weapons. Clothes or shoes with glass fragments are wrapped in paper and submitted to the laboratory. In hit-and-run cases, the glasses should be stored in different containers. Large fragments should be placed in boxes that are insulated to prevent more breakages. The boxes should be sealed and marked. After analysis in the laboratory, this evidence should be stored in the police evidence room.

Controlled substances and drugs

These are found in places where people abuse or sell drugs, which leads to drug related felonies. They are sealed, marked, and then taken to the laboratory for analysis. They are mostly stored in evidence rooms, and some are later destroyed in some instances. As seen above there are different types and kinds of physical evidence, and different methods of collecting this evidence. By the nature of physical evidence being very important in investigating and ultimately prosecuting suspects, great care is taken to make sure that there is no contamination.


Bergman M.M. (2009). Mixed social research: Thousand oaks California, sage publications

. Suggested Guidelines, for Establishing Evidence Response Teams: Federal Bureau of Investigation Laboratory Washington, D.C: 2010

Turvey B. (2000). A Staged Crime: A Preliminary study of 25 cases. Journal of behavioral profiling, 1(3)

Turvey B. (2008). Criminal profiling. San Diego Elserviour Science.