The Law and Credibility
by Charles K. Deak
With test results that arent obvious to the naked eye, analytical
chemists must prove their credibility. Charles K. Deak, a forensic
examiner used to defending his credibility as an expert witness,
discusses the many ways to do this in the analytical chemistry
Chemistry, particularly analytical chemistry, is a science that
is probably the least understood by lay people. They do not understand
how the composition of a metal alloy can be determined or even
the fact that the determination is based on sound scientific principles
and is not the result of some mysterious hocus-pocus or voodoo.
In many of the other sciences there is frequently some visible
evidence to support the results of the examination. For example,
on a broken part it can be pointed out that a certain dimen-sion
is too, small to make the part strong enough, or, on a bent part that
cracked, a too small bending radius can be pointed out as the
cause of the crack. Regretfully we, as analytical chemists, do
not have the luxury of presenting such visible evidence. In other
words, requestors just have to take our word for it.
They readily accept our word if it is what they expected, or it
is to their liking. However, if the results are not to the requestors
liking, it can be a different story. How many times is the analytical
chemist asked to repeat a determination because the result obtained
is just plain impossible in the requestors opinion? (In other
words, not what the requestor would like to hear.) Basically,
we, as analytical chemists, often face a credibility gap. What
we need to do is eliminate or at least greatly reduce this gap.
The Credibility of the Scientist
I am a forensic examiner who specializes with clients, particularly
in the legal profession, who have metal-related problems. As such,
I have to act as an expert in cases and from time to time have
to appear at depositions or in court as an expert witness. To
do this, I have to have credibility.
Expert witnesses in most parts of the world, especially in many
European countries, are prominent experts in their field who have
generally been appointed by the minister of justice. Theseoften
lifetimeappointees, are given the title of court expert, and
are listed on a roster from which parties involved in litigation
can select their experts. In the United States we have a completely
different system. The parties select their own experts. However,
each time experts appear in court, they have to be re-qualified..
The attorney who wants the witness to be qualified as an expert
questions him concerning his education, job-related practical
experience, specialized experience, publications, papers presented,
etc., and asks the court to recognize the witness as an expert.
Before the court rules, the opposing attorney is given a chance
to examine the witness and to point out the possible weaknesses
or flaws in the expertise of the witness. Finally, the court rules
whether to accept the witness or not.
The importance of being qualified as an expert is that only an
expert witness can state an opinion in court. All other witnesses
(referred to as material witnesses) are restricted to testifying
only about things they heard, saw, experienced, or did. (Sometimes
objections to the acceptance of a witness as an expert can take
unusual forms. In one of my early trials, I was working for the
defense lawyer in a high profile murder trial. The prosecutor
objected to me being accepted as an expert on the grounds that
I never testified as an expert in a murder trial. The judge in
his ruling stated that apart from the fact that he never testified
in a murder trial as an expert, in all other respects, the witness
has good qualifications; and if the court would accept the objection
as a valid argument, we soon would run out of experts, as nobody
could testify as an expert for the first time. He then accepted
me as an expert.)
The Credibility of the Analytical Results
Let us look at some of the factors that are involved in establishing
the credibility of analytical results. The first thing to look
at is the laboratory itself, including the work, in general, performed
there. Laboratories have been around for hundreds and hundreds
of years, operated by the alchemist at one time, and later by
chemists and other scientists. I do not believe one of the old
alchemists laboratories would impress anyone today or establish
credibility for work performed there.
International Organization for Standardization (ISO) Guide 25, General requirements for the competence of calibration
and testing laboratories, became the cornerstone of competent
laboratory operation in the last couple of decades. There are
several organizations such as the American Association for Laboratory Accreditation (A2LA), the National Voluntary Laboratory Accreditation Program (NVLAP), etc., that accredit laboratories to ISO Guide 25 (ISO
Guide 25 has recently been replaced by ISO/IEC 17025, General
Requirements for the Competence of Testing and Calibration Laboratories).
Many laboratories underwent this accreditation process to meet
their customers requirements or to comply with certain regulations,
but all did it with the hope that it would increase their credibility.
The abovementioned competence requirements delve into most aspects
of the laboratories, such as organization, personnel qualifications,
equipment maintenance, calibration, standards, reference materials,
laboratory reports, records, etc. Naturally, it has to be realized
that a certification does not guarantee that the laboratory performs
good work, only that it has the facilities, talent and capability
to perform good work.
Another very practical endeavor for a laboratory is to participate
in an inter-laboratory proficiency testing program, in which all
participating laboratories receive identical samples for analysis.
(ASTM has one such Proficiency Testing Program.) The results of
the various participating laboratories (identified only by code
numbers) are tabulated, and the laboratories can evaluate how
they compare to their peers. This, incidentally, is part of any
reputable laboratory accreditation program.
One of the most important factors that affect not only the credibility
but also the accuracy and precision of an analyses is the method
or procedure used to perform it. The procedure must produce accurate
and repeatable results. It must be reliably interference- free
or appropriate techniques for correction of interferences must
be incorporated in the procedure. Another very important factor
is that the procedure must be written down in unambiguous language
that is understandable and can be readily followed by a person
versed in the art, and the procedure must be tested by a panel
of experts and statistically evaluated.
Such procedures are referred to as standards. Standards are written
either by government, by certain larger commercial corporations
where they form part of the purchase specifications, and mostly
by independent, consensus standard writing organizations.
One of the largest such organizations is ASTM, and, for metal
and ore analysis specifically, ASTM Committee E01 on Analytical Chemistry for Metals, Ores, and Related Materials.
By rigorously following an appropriate standard, a person versed
in the art should be able to obtain accurate results. This is
one of the reasons that test certificates issued by the laboratory
are supposed to list the standard(s) used for the analysis, and
also any deviation from the standard.
The Credibility of Instruments
Since many of todays procedures used are instrumental ones, we
have to have a means to calibrate the instrument used and to verify
the results. First of all, the instruments have to be calibrated
generally with some materials similar to the ones being analyzed,
and the calibrations have to be verified by analyzing appropriate
samples with known composition. These samples, in which one or
more properties are well characterized, are referred to as reference
materials. These reference materials have to be checked in accordance
with approved standards for homogeneity. They have to be tested
and certificates issued in accordance with accepted standards.
Certified reference materials (or CRMs) are the highest grade
reference materials produced by recognized national laboratories.
CRMs produced by the National Institute of Standards and Technology are marketed under the registered trade name of standard reference
material (or SRMs), and have high worldwide acceptance and reputation.
To sum it all up, if one performs the analysis of metals, ores,
etc., in accordance with the above outlined criteria in a certified
laboratory that produces good results during regularly performed
interlaboratory proficiency testing programs, uses appropriate
standards to perform the tests, uses appropriate reference materials
for calibration and verification, issues appropriate reports,
and can back this all up with the appropriate and required records,
one should have no problems achieving credibility. //