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Metal Analysis

The Law and Credibility

by Charles K. Deak

With test results that aren’t 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 lab.

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 requestor’s 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. These—often lifetime—appointees, 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 alchemist’s 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 today’s 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. //

Copyright 2001, ASTM

Charles K. Deak, president of C.K. Deak Technical Services, Inc., is a board certified forensic examiner. As such, he has testified in several cases in federal, state, and local courts regarding analysis of metals and related materials. He is chairman of ASTM Subcommitteee E01.21 on Reference Materials, Proficiency Testing, and Laboratory Accreditation.


This paper was presented on March 4, 2001, at the Pittsburgh Conference on Analytical Chemistry (“PITTCON 2001”) in New Orleans, La.