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Hairs, Fibers, Crime, and Evidence Part 2: Fiber Evidence

Douglas W. Deedrick

Unit Chief

Trace Evidence Unit

Federal Bureau of Investigation

Washington, DC

Introduction | Fiber Evidence | Natural Fibers | Man-Made Fibers |

Fiber Color | Fiber Number | Fiber Location | Fabrics |

Fabric Type | Fabric Source Determination |

Fiber Transfer and Persistence | Nature of Contact |

Multiple Fiber Associations | Fiber Evidence: Assigning Significance

Introduction

Placing a suspect at the scene of a crime is an important element in criminal investigation. This can be achieved through the location of textile fibers similar to those from the victim's clothing or the crime scene on the clothing of the suspect, or through the discovery of fibers like those in the suspect's clothing at the crime scene.

Textile fibers can be exchanged between two individuals, between an individual and an object, and between two objects. When fibers are matched with a specific source (fabric from the victim, suspect, and/or scene), a value is placed on that association. This value is dependent on many factors, including the type of fiber found, the color or variation of color in the fiber, the number of fibers found, the location of fibers at the crime scene or on the victim, and the number of different fibers at the crime scene or on the victim that match the clothing of the suspect.

Whether a fiber is transferred and detected is dependent on the nature and duration of contact between the suspect and the victim or crime scene, the persistence of fibers after the transfer, and the type(s) of fabric involved in contact.

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Fiber Evidence

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. 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.

As discussed previously, 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. Fibers can also transfer from a fabric source such as a carpet, bed, or furniture at a crime scene. These transfers can either be direct (primary) or indirect (secondary). A primary transfer occurs when a fiber is transferred from a fabric directly onto a victim's clothing, whereas a secondary transfer occurs when already transferred fibers on the clothing of a suspect transfer to the clothing of a victim. An understanding of the mechanics of primary and secondary transfer is important when reconstructing the events of a crime.

When two people come in contact or when contact occurs with an item from the crime scene, the possibility exists that a fiber transfer will take place. This does not mean that a fiber transfer will always take place. Certain types of fabric do not shed well (donor garments), and some fabrics do not hold fibers well (recipient garments). The construction and fiber composition of the fabric, the duration and force of contact, and the condition of the garment with regard to damage are important considerations.

An important consideration is the length of time between the actual physical contact and the collection of clothing items from the suspect or victim. If the victim is immobile, very little fiber loss will take place, whereas the suspect's clothing will lose transferred fibers quickly. The likelihood

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