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
