Fiber Evidence

Sometimes the smallest piece of evidence found at a crime scene can be the thing that provides a major clue or becomes a major factor in winning a conviction. Hairs found on a victim routinely point to a suspect and because DNA analysis can often be done, this provides a definitive identification of the perpetrator. Likewise, fibers obtained from victims clothes or in the area of the crime scene can guide investigators in the direction of a particular suspect. Fiber analysis by the forensic laboratory has become increasing important in many cases. A caution, however, is that fiber evidence unlike DNA is not unique. It can not definitively identify a suspect but it can serve to narrow the field of potential suspects.

Color Me Busted -Sometimes fiber analysis can prove to be very strong evidence in a case. This was particularly true in the case of the abduction and murder of Kristen Harrison in Ohio in 1982. The young girl was raped, murdered and left in a field about thirty miles from her home. The forensic investigators on the scene found orange fibers in her hair. These fibers were polyester and had a distinctive shape; a shape similar to fibers used in carpet. These fibers were relatively unique because of their color and shape. They were also similar to orange fibers found on a twelve year old girl found murdered eight months prior in the same general area.

Initially these orange fibers did not lead investigators anywhere. A few months later a young woman was abducted by a man and held hostage in his home where he tortured her and indicated that he planned to kill her. She was able to escape and went to the police. On investigation it was observed that he drove a van similar to the one a witness had reported Kristen Harrison had been forced into. The van had unique orange carpeting in the back. On analysis the fibers matched those found on Harrison’s hair. The color of this fiber was so unique that the lab was able to identify the dye used and trace it to a specific carpet manufacturer. Less than seventy-five yards of this carpeting had been shipped to this particular area of Ohio. This greatly limited the number of potential suspects. Eventually, in conjunction with other evidence that provided a strong link to the owner of this van he was convicted for the murder of the eleven year old girl.

Fiber Type and Transfer - While fibers are important pieces of trace evidence, we can’t say that a specific fiber came from a specific perpetrator or location. As such, fiber evidence is considered circumstantial evidence and strengthens any additional circumstantial or solid evidence against a suspect. When two objects come in contact during the commission of a crime there is transfer of material from one individual to another. Usually small fabric fibers are transferred from the perpetrator to the victim. This is direct or primary transfer. If a fiber is transferred to a victim from the rug in a car trunk or from a blanket this is considered indirect or secondary transfer. It is also possible for fiber materials to be transferred from the victim to the suspect clothing but this is a less frequent source of evidence.

At the crime scene fibers are collected with tweezers or a gloved hand and placed in small plastic evidence collection bags. The bags are labeled appropriately and sent to the lab for analysis. Fibers found on the victims clothes or hair are removed and sent for analysis in a similar manner. Fibers may be classified as Natural which includes, cotton, wool, lama, alpaca, or other animals. Natural fibers can also come from plant materials like flax, hemp or kapok among others. A third class of fibers is man-made fibers like nylon, polyester, rayon and acrylics.