A crime laboratory usually includes five basic services:

☛ Physical Science unit: uses the principles of chemistry, physics, and geology to identify and compare physical evidence;

☛ Biology unit: applies knowledge of biological sciences in order to investigate blood samples, body fluids, hair and fiber samples;

☛ Firearms unit: investigates discharged bullets, cartridge cases, shotgun shells and ammunition;

☛ Document unit: provides the skills needed for handwriting analysis and other questioned document issues; and

☛ Photographic unit: applies specialized photographic techniques for recording and examining physical evidence.

Additional services may include toxicology, fingerprint analysis, voiceprint analysis, evidence collection and polygraph (lie detector) administration.