Biological Evidence At Crime Scenes

The different types of biological evidence discussed in the previous section can be used to associate or to exclude an individual from involvement with a crime. In particular, the direct transfer of DNA from one individual to another individual

Table 3.1

Sources of biological materials used for PCR-based DNA typing.

Material

Reference

Blood and blood stains Semen and semen stains Bones Teeth

Hair with root Hair shaft

Saliva (with nucleated cells)

Urine

Feces

Debris from fingernails Muscle tissue Cigarette butts Postage stamps Envelope sealing flaps Dandruff Fingerprints

Personal items: razor blade, chewing gum, wrist watch, ear wax, toothbrush

Budowle et al. (1995) Budowle et al. (1995) Gill et al. (1994) Alvarez Garcia et al. (1996) Higuchi et al. (1988) Wilson et al. (1995) Sweet et al. (1997)

Hopwood et al. (1996)

Wiegand et al. (1993)

Hochmeister (1998)

Hochmeister et al. (1991)

Hopkins et al. (1994)

Word and Gregory (1997)

Herber and Herold (1998)

Van Oorschot and Jones (1997)

or to an object can be used to link a suspect to a crime scene. As noted by Dr. Henry Lee (Lee et al. 1991, Lee 1996), this direct transfer could involve:

1. The suspect's DNA deposited on the victim's body or clothing;

2. The suspect's DNA deposited on an object;

3. The suspect's DNA deposited at a location;

4. The victim's DNA deposited on suspect's body or clothing;

5. The victim's DNA deposited on an object;

6. The victim's DNA deposited at a location;

7. The witness' DNA deposited on victim or suspect; or

8. The witness' DNA deposited on object or at location.

DNA evidence collection from a crime scene must be performed carefully and a chain of custody established in order to produce DNA profiles that are

The U.S. Postal Service began using electron-beam irradiation of mail (for some ZIP postal codes in Washington, DC) as a protective measure against terrorism with biological agents following the anthrax attacks on the Senate Office Building in October 2001. The irradiation is performed at levels demonstrated to cleave microbial DNA and prevent passage of harmful materials such as anthrax.

However, recovering human DNA and developing a DNA profile from licked stamps and envelope flaps can sometimes be important in tracing the origin of threatening letters. Two studies have been published recently examining the effects of electron-beam irradiation on buccal-cell DNA (Castle et al. 2003, Withrow et al. 2003). Both studies concluded that while electron-beam irradiation reduces the yields and quality of DNA extracted from buccal-cell collections, the short tandem repeat DNA typing systems used in human identity testing could still be successfully amplified.

Sources:

Castle, P.E. et al. (2003) Effects of electron-beam irradiation on buccal-cell DNA.

American Journal of Human Genetics, 73, 646-651. Withrow, A.G. et al. (2003) Extraction and analysis of human nuclear and mitochondrial DNA from electron beam irradiated envelopes. Journal of Forensic Sciences, 48, 1302-1308.

DNA recovery from irradiated samples meaningful and legally accepted in court. DNA testing techniques have become so sensitive that biological evidence too small to be easily seen with the naked eye can be used to link suspects to crime scenes. The evidence must be carefully collected, preserved, stored, and transported prior to any analysis conducted in a forensic DNA laboratory. The National Institute of Justice has produced a brochure entitled 'What Every Law Enforcement Officer Should Know About DNA Evidence' (see http://www.ojp.usdoj.gov/nij) that contains helpful hints for law enforcement personnel who are the first to arrive at a crime scene.

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