The FDA publishes Guidance for Industry documents. One such document is for the Investigating Out-of-Specification (OOS) Test Results for Pharmaceutical Production which details guidance that applies to chemistry-based laboratory testing of drugs regulated by CDER. It is directed toward traditional drug testing and release methods.
The link below is to a nice summary on the legal decision on Barr Laboratories practices with OOS results.
The main finding being that:
Barr’s practice of responding to an out-of-spec result by testing twice more and taking “best two out of three” is insupportable and unscientific, and is not GMP.