[pandaman]

Base rate fallacy will start applying when the test's false positive rate is comparable to the frequency of the event. In the US cops usually don't show up at all when called, for cops to show up and do drug testing somebody needs to do something outrageous and the probability of the same person doing drugs is pretty high IMHO so the test with 4% error rate is going to be just fine. Of course, for the drugs conviction, the actual drugs need to be found but from what I understand, this article is about somebody arrested based on a drug test, then charged with a different crime and a sneaky lawyer, unable to fight the charges, trying to throw the case based on the "faulty test".