Physical evidence
Physical evidence refers to tangible objects that can be perceived through the senses and are instrumental in legal contexts, particularly in criminal and civil investigations. This type of evidence plays a crucial role in forensic science, as it can establish whether a crime has occurred or whether a product is defective. Examples of physical evidence include biological materials like blood and saliva, which can provide DNA, as well as various forms of impression evidence such as fingerprints and tire tracks. Additionally, physical evidence can be categorized as class evidence, which links back to a group of items, or individual evidence, which can be traced to a specific individual or object.
Forensic analysis of physical evidence can reveal connections between suspects and crimes or support the exoneration of innocent individuals. It encompasses a wide range of materials, including trace evidence like fibers and gunshot residue, as well as weapons used in crimes. Interestingly, while physical evidence is primarily considered nonliving, it can originate from living entities including humans and animals. Moreover, the realm of physical evidence has expanded to include devices and hardware involved in cyber crimes, acknowledging the evolving nature of evidence in the digital age. However, it should be noted that testimonial, documentary, and digital evidence are generally not classified as physical evidence.
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Physical evidence
DEFINITION: Objects that are identifiable through several of the senses and are often used to prove facts in a court of law, such as establishing that a crime has been committed or a defective product has caused harm.
SIGNIFICANCE: Forensic scientists analyze physical evidence collected from crime scenes and other locations to determine whether and how the evidence is relevant to criminal and civil investigations. Physical evidence may link suspects to crimes or civil wrongs or exonerate innocent people.
Generally, physical is defined as nonliving, although the sources of such evidence may be humans, animals, or plants. Body fluids—such as blood, semen, and saliva—and the DNA (deoxyribonucleic acid) extracted from them are examples of biological or serological evidence that may be considered physical evidence. Physical evidence is often divided into class evidence, which can be linked only to a type (or class) of items, and individual evidence, which can be linked to a specific individual, item, or civil wrong.
Physical evidence may include things that can be seen, whether with the naked eye or through the use of magnification or other analytical tools. Some of this evidence is categorized as impression evidence, including bite marks, fingerprints, footprints, knife cuts, tire tracks, and tool marks. Pattern evidence, a subcategory of physical evidence, might include blood spatter and burn patterns. Trace evidence is, in most cases, microscopic physical evidence that includes fibers, flakes, gunshot and bomb residue, hair, paint, plastic, pollen, soil, dust, and small fragments of physical objects such as glass, fingernails, fluids, and wood. Trace evidence might also include poisons that can be discovered only through body organ and tissue sampling.
Some physical evidence may be detected by smell or taste, often through the use of trained dogs. Such evidence might include accelerants, bombs, chemicals, and drugs. Among the most obvious kinds of physical evidence are weapons and other objects used to commit crimes, such as blunt instruments, guns and bullets, knives, ropes, and ligatures. Forged or altered documents are also physical evidence, as are actual objects or defective parts that caused harm in civil cases.
Forensic scientists are sometimes involved in gathering evidence of cyber crimes and civil wrongs committed with the use of computers. Although digital data evidence is not technically physical evidence, the physical objects used to create and transmit such data evidence are. Thus, physical evidence includes computer hardware and peripherals as well as electronic devices such as cell phones, tablets, and personal digital assistants.
Among the types of evidence generally not considered to be physical evidence are testimonial evidence from eyewitnesses, documentary evidence such as drawings or diagrams depicting crime scenes, digital evidence, audio evidence, and behavioral evidence from profiling.
Bibliography
Byrd, Mike. Crime Scene Evidence: A Guide to the Recovery and Collection of Physical Evidence. Wildomar, Calif.: Staggs, 2001.
"Crime Scene and DNA Basics for Forensic Analysts: Type of Evidence." National Institute of Justice, 15 June 2023, nij.ojp.gov/nij-hosted-online-training-courses/crime-scene-and-dna-basics-forensic-analysts/evidence-crime-scene/types-evidence. Accessed 19 Aug. 2024.
Fisher, Barry A. J., and David R. Fisher. Techniques of Crime Scene Investigation. 8th ed. Boca Raton, Fla.: CRC Press, 2012.
Lee, Henry C., and Howard A. Harris. Physical Evidence in Forensic Science. 3d ed. Tucson, Ariz.: Lawyers & Judges Publishing, 2011.
Osterburg, James W., and Richard H. Ward. Criminal Investigation: A Method for Reconstructing the Past. 7th ed. Waltham, Mass.: Anderson, 2014.
Owen, David. Hidden Evidence: Forty True Crimes and How Forensic Science Helped Solve Them. Richmond Hill, Ont.: Firefly Books, 2000.
Rao, Piyush K., et al. "Physical Evidence and Their Handling." Technology in Forensic Science: Sampling, Analysis, Data and Regulations, 28 Aug. 2020, doi.org/10.1002/9783527827688.ch4. Accessed 19 Aug. 2024.