Placing a suspect at the scene of a crime is what it is all about. One of the ways that this can be done is by locating textile fibers similar to those from the victim’s clothing or the crime scene on the clothing or person of the suspect or discovering fiber evidence at the crime scene that can somehow be traced back to the suspect.
Fibers are Trace Evidence
Fibers are considered a form of trace evidence that can be transferred from the clothing of a suspect to the clothing of a victim during the commission of a crime. Textile fibers can also be transferred from rugs or blankets; between two individuals; between an individual and an object or between two objects
Locard's Exchange Principle
Locards Theory involves evidence transfer was postulated by 20th century forensic scientist Edmond Locard. Locard’s principle which is essentially applied to crime scenes, states that where the perpetrator(s) of a crime come into contact with the scene, they will both bring something into the scene and leave with something from the scene. Every contact leaves a trace.
What is Fiber Evidence?
According to Douglas W. Deedrick, Unit Chief of the Trace Evidence Unit, Federal Bureau of Investigation, Washington, DC, a fiber is the smallest unit of a textile material that has a length many times greater than its diameter. Fibers can occur naturally as plant and animal fibers, but they can also be man-made.
He explains that a fiber can be spun with other fibers to form a yarn that can be woven or knitted to form a fabric. The type and length of fiber used, the type of spinning method, and the type of fabric construction all affect the transfer of fibers and the significance of fiber associations.
“This becomes very important when there is a possibility of fiber transfer between a suspect and a victim during the commission of a crime,” Deedrick says.
Primary and Secondary Transfers of Fibres
There are many ways that fibers can be transferered in the commission of a crime. They can transfer from a fabric source like a carpet, bed, or furniture at a crime scene. This is called direct or primary transfer of forensic fibers.
A secondary transfer occurs when already transferred fibers on the clothing of a suspect transfer to the clothing of a victim. For instance, if fibers from a carpet in the suspect's bedroom get transferred to the victim, without the victim ever having been in that bedroom. Understanding the mechanics of primary and secondary transfer is important when reconstructing the events of a crime.
Is There Always Fiber Evidence at a Crime Scene?
When two people come into contact or when a person comes into contact with an item at the crime scene where fiber transfer could take place, one would think that it always does, after all, what about Locard’s Exchange Principle?
Unfortunately fiber transfer doesn’t always take place. Certain types of fabric do not shed well (donor garments), and some fabrics do not hold fibers well (recipient garments).
Important consierations in fiber transfer are:
- the construction and fiber composition of the fabric
- the duration and force of contact
- the condition of the garment with regard to damage
Sources:
Forensic Fibre Analysis - "Truth is smaller than fiction"; Issue 1 of the Forensic Access Newsletter "Benchmark".
Hairs, Fibers, Crime, and Evidence Part 2: Fiber Evidence by Douglas W. Deedrick, Unit Chief of the Trace Evidence Unit, Federal Bureau of Investigation, Washington, DC.
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