The trouble with probation drug testing is that the probationeer has virtually relinquished the rights normally enjoyed by persons taking an employment test, including the right to a fair drug test.
Many probation departments, in an effort to keep costs down, use cheap screens with no confirmation test. These cheap screens are prone to false positives. A person taking certain OTC/scripted meds can result in false positives for THC or any other drug tested on a given panel. Without the confirmation GC/MS to disprove the false positive, the donor can get sent back to jail for simply taking the wrong medications.