Trace Evidence: Definition, Analysis & Examples

Lesson Transcript
Instructor: Rachel Leintz

Rachel has taught in the fields of Forensic Science and Criminal Justice for over 7 years and has a master's degree in Forensic Science

Trace evidence is something small like hair, fiber, soil, or fingerprints that is transferred from one person to someone else or to a place. Explore the definition, analysis, and examples of trace evidence. Updated: 11/20/2021

Trace Evidence Defined

A man runs through a dark, cold forest in the middle of the night. His heart is pounding. He's sweating. In his mind, he sees flashes of his victim, lying on the ground. No one saw him. No one knows what he did. He didn't leave anything for the police to find. He's gotten away with it . . . Or has he?

The word 'trace' means small or minute. To a forensic scientist, trace evidence refers to evidence that is transferred from one person to another person or place. In the forensic world, this concept is known as Locard's Exchange Principle. The man running through the woods may have taken precautions not to be seen by anyone, but there are several different kinds of trace evidence that can be collected from a crime scene that could lead to his arrest.

Trace evidence types commonly collected from crime scenes include:

  • Hairs
  • Fibers
  • Glass
  • Plant material
  • Paint chips or transfers
  • Soil
  • Fingerprints

Let's look at how some of these evidence types could be used by forensic examiners to catch the criminal running through the woods in our example.

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  • 0:01 Trace Evidence Defined
  • 1:08 Trace Type: Hair
  • 2:13 Trace Type: Fiber
  • 3:06 Trace Type: Soil
  • 3:44 Trace Type: Fingerprints
  • 4:59 Lesson Summary
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Trace Type - Hair

If a hair or hairs are found at a crime scene, there are several different characteristics forensic scientists can examine to determine information about the person the hair belongs to. For example, the center of a hair shaft is called the medulla. Forensic scientists can examine a piece of hair and identify the type of medulla in the shaft. The medulla can be continuous, interrupted, fragmented, solid, or it can not show up at all. The examiner can then compare the hair to known samples, taken from victims or suspects.

Forensic Scientists can also examine hair for different characteristics to determine what part of the body it came from. For example, they can determine if a hair came from someone's head or from a different part of the body, like a beard. The examination of hair can also determine if it came from an animal or a human. If a hair is forcibly removed, yanked or pulled out, the entire hair follicle may be present. The follicle may have blood and tissue attached to it, which could be examined for possible DNA evidence. So while the criminal in our story is sure no one saw him, is he sure that none of his hair was transferred to the victim?

Trace Type - Fiber

A fiber is the smallest part of a textile or cloth. Forensic examiners can collect fibers from a crime scene, a victim, or a suspect. Fibers have special characteristics that can tell an examiner the type of fabric the fiber came from. When forensic examiners collect fibers, they will try to answer several questions. First, they will try to determine the type of fiber. What is the fiber made of? Is it a natural fiber, like cotton? Or is it a synthetic, or man-made, fiber like polyester? Next, they will look at the color of the fiber. Some colors can be very specific, and examiners can actually tell the type of dye used on a particular fiber. If larger samples are present at a crime scene or on a victim, forensic examiners can also examine characteristics of these larger pieces of evidence. For example, if the victim in our story tore a piece of the man's shirt during the struggle, the weave of that scrap could be compared to the weave of the suspect's torn shirt.

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