Collection of Physical Evidence at a Crime Scene

Chapter 2/ O’Connor

Physical Evidence

• Can range from massive objects to microscopic traces.

• Some crime scene evidence is obvious and others will not be discovered until items are examined in the forensic lab

• Minute traces of blood, hairs, and fibers may be revealed when garments are searched in the laboratory or from vacuum sweepings collected at the scene.

• It may be necessary to take custody of all clothing worn by the participants in a crime. Sweepings from each area of a crime scene must be collected and packaged separately.

Crime Victims as a collection site

• Fingernail scrapings from individuals who were in contact with other individuals may contain minute fragments of evidence that can link an assailant to a victim.

• Fingernail scrapings are to be taken with a blunt instrument, like a toothpick. The scrapings are to be collected and packaged separately for later microscopic examination.

Forensic Vacuums

Autopsy

• If there is a deceased victim, the body will be autopsied by a medical examiner or coroner to collect evidence.

• They will be working to determine the cause of death, as well as collecting evidence.

Collected, cataloged and sent to forensic lab:

1. Victim’s clothing

2. Fingernail scrapings

3. Head and pubic hairs

4. Blood (for DNA typing)5. Vaginal, anal, and oral swabs (in sex related cases)

6. Recovered bullets from the body

7. Hand swabs from shooting victims (for gunshot residue analysis)

Processing Evidence

• Physical evidence must be handled in a way that prevents any change from taking place between the time it is removed from the crime scene and received by the laboratory.

• Changes can arise through contamination, breakage, evaporation, accidental scratching, bending, or loss, due to improper or careless packaging.

Blood, hairs, fibers, soil particles, and other types of trace evidence should not be removed from garments, weapons, or other articles. The entire object should be sent to the lab for processing.

Exceptions to the rule

• If evidence is found adhering to a large structure, such as a door, wall or floor; remove the specimen with a forceps or appropriate tool. In the case of a bloodstain, one may either scrape the stain off the surface or transfer the stain to a moistened swab, or cut the area of the object bearing the stain.

• Each different item or similar items collected at different locations must be placed in separate containers!

• Packaging evidence separately prevents damage through contact and prevents cross-contamination.

Maintaining the Chain of Custody

• Chain of custody must be established when evidence is presented in court as an exhibit.

• Every person who handled or examined evidence must be accounted for. Failure to do so can lead to questions of authenticity and integrity of evidence.

• There are standard procedures for recording location of evidence, marking for identification, and completion of evidence submission forms.

Recording

• Once a container is selected to be used for collection it must be marked for identification

A minimum record will show:

• The collector’s initials

• Location of the evidence

• Date of collection

• If turned over to another individual, every transfer must be recorded in notes and on the forms.

Standard Reference Samples

• Collection must include not only evidence, but standards for comparison. You must know what you are trying to match or eliminate from the crime scene for use in the laboratory.

• Example: hairs, blood, fibers, or soil samples.