Day-in and day-out, police officers deal with evidence—hard, physical evidence. It is the duty of these officers, and the department as a whole, to protect and control the physical evidence for a case. If evidence is missing or tainted, or if the chain of custody is broken, that evidence cannot be used in court. This can, in turn, cause a mistrial—causing the case to be thrown out and the accused to be released. Inmates have been released from prison, and the community sued for false imprisonment, all due to the mishandling physical evidence. Physical evidence is the key to a successful prosecution, and the integrity of every department depends on its proper collection and handling.
What is Physical Evidence?
The Locard’s Exchange Principle explains that a perpetrator always leaves evidence behind because of the objects or people they come in contact with, or objects they may have taken from the crime scene. Different types of physical evidence come in all shapes and sizes and can either be considered corroborative evidence by supporting a theory or circumstantial evidence by indirectly inferring a conclusion to the crime.
The subtle type of physical evidence, trace evidence, is small but measurable. It is typically noticed after a closer examination upon larger pieces of physical evidence and can sometimes require a microscope or other instrument. Although smaller and sometimes hard to see, trace evidence can be crucial to a crime scene and investigation. Proper collection, testing, and storage can make or break a case. An example of trace evidence would be small blood stains on an article of clothing.
Examples of Types of Physical Evidence
Different types of physical evidence require various collection techniques to avoid contamination and damage. We’re listing some of the main types of physical evidence police encounter and how they can help investigators in solving crimes.
- Paint– The chemical and physical analysis of the type of paint can be used to match evidence to a suspect by examining characteristics such as color, number of layers, etc.
- Glass– Tint, color, chemical composition, density, and other properties of a glass can be examined in particles found at various crime scenes such as a hit-and-run, murder, breaking and entering, etc.
- Explosives– By using chemical analysis and tracing the materials of explosives can lead to a suspect’s work, home, or lead to another connection.
- Ballistics– Analysis of the characteristics of firearms, gunshot residue, ammunition help investigators find matches between the evidence found at the crime scene and suspects.
- Dust and dirt – Dust, dirt, pollen, plants, and more left at a crime scene can be used to determine where a suspect has traveled from.
- Impression Evidence– There are 3 types of impression evidence: shoe prints and tire tracks, bite marks, and tool marks. Each of these can use either one or a combination of the following collection tactics, such as photographs, lifting with tape, or casting with plaster. When the proper techniques are used, impression evidence can help investigators match to other items or suspects.
- Fingerprints– Investigators will use an Automated Fingerprint Identification System to analyze between the 3 types of fingerprint patterns to find a match.
- Questioned Documents– These documents include ransom notes, letters, watermarks, and more, all of which can provide useful clues.
- DNA, body fluids, hair, etc.– All of these can provide information about a crime and be tested for matches to other samples.
The Integrity of Types of Physical Evidence
Protecting physical evidence, especially trace evidence, and using specialized techniques, are crucial to an investigation. When you use high-quality evidence tracking software, you’re able to track every aspect of each piece of evidence. Using gloves during handling, tracking where and when evidence has been moved, who has had access to evidence, and storing it properly are all pivotal to avoiding potential damage. The PMI Evidence Tracker™ was “Designed by Cops for Cops,” because we know the critical role that police and investigators play in collecting and storing evidence. Keep detailed information about each type of physical evidence with our complete system that comes with tracking software, barcode scanners, labels, and more. See how the PMI Evidence Tracker™ can streamline inventory workflow and maximize efficiency by getting in touch with us today.