In a series of posts, I am going to introduce the reader to the existence of ISO 17025 and its importance.  I am going to introduce it in bite-sized bits for easy digestion.  Just like all matters of learning, knowledge is incremental over time and builds upon previous exposure.

In our first post we answered the question: What is ISO 17025?

The next post we answered the question: Why do we need standards? Why ISO 17025 and policy, procedures and instructions matter.

Then we answered the question: Why is ISO 17025 so important to us in forensic science?

Just a little while ago, we asked and answered: Why should the criminal defense community care about ISO 17025?

Today we examine how ISO 17025 provides a simple method to develop themes to cross-examine experts.

How do you cross-examine an expert?

The above question I get asked a lot. So much so that I have been invited to speak on the topic before the Texas Criminal Defense Lawyers Association (TCDLA) at their seminar entitled “Cross Examination,” which will feature

• Racehorse Haynes
  
• Dick DeGuerin
• Gerry Goldstein
• Kent Shaefer
• Terry MacCarthy-  the father of modern cross examination. Terence MacCarthy is synonymous with effective cross-examination. For 41 years, he has headed the Federal Defender’s Office in Chicago and is among the top CLE instructors in the nation owing to his lectures on cross-examination technique. MacCarthy is the author of MacCarthy on Cross-examination.
• Dan Cogdell-only person to gain an acquittal in the Enron prosecutions
  

As one will discover in our later posts, the specific provisions and requirements of ISO 17025 naturally gives defense attorneys  not only great cross-examination themes, but most importantly a proverbial treasure map of the laboratory itself that will allow us to find the necessary information to populate these themes with potentially crippling information from the laboratory’s own documents and reports.

(Above: a clip from the movie “A Few Good Men”-if you understand ISO 17025, you will see if they can handle the truth)

ISO 17025 lately has been presented to the criminal defense field in terms of metrology. However, it extends past metrology, and indeed goes into the heart of laboratory science and the scientific method itself. If properly understood, ISO 17025 provides for substantive cross and themes that any defense attorney can use to expose critical potential issues. These themes include:

• The limitations of the person performing the test (for example, the qualifications, the experience and the formal knowledge of the analyst)
• The credentials and authority of those on the bench and those who supervise the bench;
• The limitations of the assays;
• The validation, or lack thereof, of the method;
• The assumptions made by the method;
• The uncertainty in the qualitative result and the Uncertainty Measurement (UM) in terms of the quantification of the test result; and
• The importance of sampling versus sample selection

All of these, it is suggested, should be the minimum themes that one uses in crossing any proffered expert.