We know government labs create a conveyor belt mentality in their testing process. They force the techs to push through as many samples as they can, and they fail to properly train these techs on what to look for, and how to ensure there are no problems in the run. When a tech sees a problem, they do not see a problem, because they have not been trained to identify it as a problem. The same can be said for their understanding of Method Validation and Proficiency testing.
In Analysis of the Relationships Between Proficiency Testing, Validation of Methods and Estimation of Measurement Uncertainty, by Albano and Caten, Accred Qual Assur (2016) 21:161-166, they point out the necessity of these processes to ensure quality results. Method validation is important, and is "the confirmation, through objective evidence, that the specific measurement requirements are met for an intended use." It looks for where lab errors can occur. And "therefore, it is important to validate every stage of the test or calibration in the laboratory environment." So, did they properly perform the method validation, and have they checked it with their Proficiency testing.
Forensic crime labs rely upon institutional knowledge, and work performed years ago if ever, to show they have performed method validation. They then attempt to use what they call proficiency testing to justify their results. However, if they have not properly performed, or can prove, the existence of the method validation, they cannot prove the reliability of the results. Another jewel in the forensic library.