- During the course of performing everyday activities, humans and animals shed hair and fiber evidence from their bodies, clothes and from other objects or materials with which they make contact. Forensic analysis may be used to examine such trace evidence to theorize about the activities of persons unable or unwilling to explain the purpose of their presence at a scene that is being investigated. Such analysis techniques have been employed by anthropologists interested in reconstructing events experienced in the past, as well as by crime scene investigators who have used carpet fibers from the car of a serial killer to draw connections between the killer and his victims, who contained the fibers on their corpses.
- Standardized collection and preservation techniques is critical when attempting to collect and preserve hair and fiber evidence. Such evidence is painstakingly collected by investigators, who are trained not to taint any evidence that they find. Agents for the Indianapolis-Marion County Forensics Agency are instructed to collect hair and fiber evidence with the aid of tweezers and combs. Such evidence must be sealed in bags or containers before being transported to a storage facility.
- Fine details of hair and fiber specimens are analyzed in laboratory settings using microscopy technology. Traditionally, a comparison microscope, constructed from two compound microscopes, has been used to examine hairs and fibers. With the advent of computerized technology, forensic investigators are also using advanced algorithms to analyze such evidence.
- Analysis of hair and fiber evidence permits forensic investigators to observe the presence of certain distinctive characteristics, aiding in the process of identification. Human hairs contain information about a subject's race, age and whether the subject is male or female. Dyes used in hair or fiber can also be important clues as to the nature of their sources.
- While forensic study of hair and fiber evidence is able yield significant information, results gleaned from such studies are rarely considered conclusive. According to Douglas W. Deedrick, Unit Chief of the Federal Bureau of Investigation's Trace Evidence Unit, "it is difficult to establish a statistical probability for a particular association due in part to the lack of reliable quantitative assessments of the microscopic characteristics present in hairs." Nevertheless, DNA that may be extracted from a hair can be tested, providing results that are considered accurate. By contrast, fiber evidence must usually be associated with an alleged source by means of a process of statistical elimination.
