There are several types of proficiency tests, with the primary distinction among them being whether the examiner is aware that he or she is being tested (an open or declared test) or does not realize that the sample presented for analysis is a test sample and not a real case (a blind test). Tests can be generated externally, by another laboratory (sometimes called an interlaboratory test), or internally. Another type of testing involves random case reanalysis, in which an examiner’s completed prior casework is randomly selected for reanalysis by a supervisor or another examiner.30

Interlaboratory testing can be conducted for a number of purposes:

  1. to determine the performance of individual laboratories for specific tests or measurements and to monitor laboratories’ continuing performance;

  2. to identify problems in laboratories and initiate remedial actions, which may be related to, for example, individual staff performance or the calibration of instrumentation;

  3. to determine the performance characteristics of a method and to establish the effectiveness and comparability of new tests or measurement methods; or

  4. to assign values to reference materials and assess their suitability for use in specific tests or measurement procedures.31

Blind proficiency testing is recommended, but not required, by ASCLD/LAB—not as a way to determine error rates, but as a more precise test of a worker’s accuracy. Initially, mandatory blind testing was proposed as part of the federal DNA Identification Act. A Department of Justice (DOJ) panel designed blind tests, evaluated them, and estimated it would cost $500,000 to $1 million annually for one test per laboratory.32 In appropriate circumstances, proficiency testing should include blind testing.

ASCLD/LAB has a detailed proficiency testing program that requires all active examiners to take at least one proficiency test per year (two tests per year in DNA), that each discipline within the laboratory participate in an external proficiency test that is reviewed by a proficiency test review


Refer to ISO/IEC Guide 43-1:1997(E) Section 4 for a list of proficiency testing schemes. Refer to ASTM E 1301 Section 6 for an overview of organization and design of proficiency tests. SWGs also provide guidelines for proficiency testing in the relevant discipline.


European Network of Forensic Science Institutes. 2005. Guidance on the Conduct of Proficiency Tests and Collaborative Exercises Within ENFSI. Available at


J.L. Peterson, G. Lin, M. Ho, Y. Chen, and R.E. Gaensslen. 2003. The feasibility of external blind DNA proficiency testing. Available at

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