In trial litigation, testimonial evidence (that given by people under oath) is generally one of the more
useful means of proof. Of course, the testimony of any witness is subject to attack for its credibility,
veracity, or sometimes even admissibility.
Keep in mind that witnesses can and do serve a useful purpose to the investigator outside
of the courtroom as well. Most witnesses provide information, leads, and other insights into
the case as a whole, without ever testifying in court. Investigators see the value of witnesses in
diverse ways:
Identication of suspects.•
Narration of facts and conditions surrounding the case.•
Discussion of motive and modus operandi.•
A tool of quality control by eliminating remote suspects.•
Proof of a hunch, guess, or professional conjecture.•
Direct eyewitness information.•
Ralph F. Brislins remarkable manual, The Effective Security Ofcer’s Training Manual,
relays intelligently:
Upon arrival at the scene and once you have determined who requires rst aid, attempt to identify
anyone and everyone who may have knowledge of what occurred. Ask witnesses to remain in the area
until you have had a chance to talk to them. It is critical in this situation that you have a notebook and
pen at your disposal. Attempt to interview those persons who were actually involved, whether they are
the alleged victims or perpetrators.
Witnesses generally fall into two categories: lay and expert. An expert witness has a specialized
knowledge upon which his or her testimony emerges, such as a chemist, a DNA specialist, or a bal-
listics examiner. All other witnesses are labeled lay witnesses, those who testify to objective reality
without a scientic vein or purpose.
To illustrate, in a speeding case, a lay witness relays “He was
going fast.While the expert, holding radar results, states The radar reading was 101 mph.But
witnesses in the street serve as many purposes as there are cases. The list includes:
A witness may be the actual victim of an intentional deed.•
A witness may be a victim of a crime.•
A witness may be a personally injured party in a negligence or medical malpractice case •
or similar tort.
A witness may be an eyewitness, that is, an individual who personally witnessed the event •
and can testify to the facts and conditions.

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