Its the old story of a commercial drug testing company getting a head start in police forensics without discriminant variable testing to support its claims of a subjects’ drug use. The FBI uses this system to this day. In general, police drug testing is getting alot of criticisms these days. Of course the victims of false “positives” get the shaft. (that’s a pun, son).

https://www.wired.com/story/the-hairy-problem-with-drug-testing/

Then there is this about cocaine testing showing positive for 1 out of 10 people in a sample study in the UK.