Testimony
Testimony is the verbal statement of a witness, under oath,
to the trier of fact, that is, the judge and/or
jury. The ordinary witness can testify only on the basis
of personal knowledge of a situation gained through the
use of his five senses. He may not express opinions formed
on any other basis. The forensic scientist, on the other
hand, can testify not only on the basis of personal knowledge,
but also in the form of opinion based on his informed evaluation
of the evidence presented and scientific tests performed
and interpreted within the bounds of his skills, experience,
and ability. He is an "expert" witness as opposed to an
ordinary or "fact" witness.
There are four criteria that are generally required to qualify
a person as an expert witness. They are: educational degrees
received, number of years of occupational experience in
the field, membership in professional organizations, and
professional articles or books that the person has published.
The forensic scientist, as an expert witness, must be able
to explain complex chemical reactions, the working of scientific
instruments, or medical conditions in simple everyday language
understandable to anyone, not scientific jargon or "gobbledegook."
This is not easy. It is so difficult that before a new scientist
is allowed to testify, a mock court is held so the scientist
can learn how it feels to testify, and how to convert his
hard-earned scientific knowledge into simple terms.
The forensic scientist must be impartial and unbiased. The
forensic scientist must tell all of the truth, "the whole
truth," no matter what it is or whom it hurts or helps.
An expert opinion can be offered only if there are scientific
facts upon which to base it.
In court, the work of the forensic scientist is carefully
examined to find any flaws, whether in the test performed,
the interpretation of the results, or the science upon which
opinion is based. Whether the forensic scientist "expert"
is hired by the prosecution or defense, the opposing attorney
will try to undermine or discredit testimony which is against
his client.
The forensic witness must be qualified and knowledgeable
of both his special area of scientific knowledge and expertise
and the rules of evidence that govern the admissibility
of opinions and conclusions.
The forensic scientist often spends long hours testifying
clearly and concisely in judicial proceedings concerning
scientific information and what it means. Throughout he
must maintain a posture of impartial professionalism.
"If the law has made you a witness,
remain a man of science.
You have no victim to avenge,
no guilty or innocent person to convict or save
— you must bear testimony within
the limits of science."'
— Dr. P.C.H. Brouardel
19th Century French Medico-legalist
