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Examining the Evidence

Proficiency Testing

Weighing the Evidence > Reliability > Proficiency Testing
Anything you do in a forensic laboratory, there will be proficiency tests for it.

Testing to Improve Reliability

Laboratories undergo periodic proficiency testing to ensure that techniques remain reliable in analysts’ hands.

The proficiency testing regimen is a two-step process. The actual testing and identifying of errors is only the initial stage. In the follow-up phase, the laboratory attempts to identify the root causes of errors, and take corrective action. Proficiency testing alerts a lab to systemic issues (in protocol, environment, training, etc.) that can be explored and corrected.

Through a complex series of decisions, proficiency tests are designed, constructed, and finally implemented to evaluate and improve the reliability of results. If a test is designed to identify a compound, substance, or drug, how much of the substance should be used in the test? It may be straightforward to identify a specimen containing a milligram of the material, but much more difficult if it contains only a microgram. What’s the objective of each test? What and whom will be tested?

How often does a particular analyst make an error? This is determined or estimated, if it can be, by proficiency testing. But it’s not a perfect system. For example, it’s virtually impossible to establish a meaningful error rate for a DNA analyst, because relatively few proficiency tests are done in a year, due to the time needed to complete them.