Im sure the lab claimed 100% accuracy.

The D.C. Department of Forensic Sciences is under criminal investigation amid allegations that managers at the independent lab pressured analysts to change their conclusions, and then potentially misrepresented findings to its accrediting body, all in an attempt to essentially paper-over a years-old error.
— Read on wtop.com/dc/2021/03/first-on-wtop-dc-forensic-lab-under-criminal-investigation-over-firearms-case/