Is there a type of drug test that can detect the last time of usage?
THC leaches out of the body very slowly due to its low solubility in water compared with fat. That coupled with her previous levels of use combine to not surprise me at all that she still tested positive. Three months is the usual sort of time-frame for elimination of THC to undetectable levels. The probation officer clearly doesn’t understand the limitations of the test. No test will accurately give a time for last use of a drug with such a long half-life in the body as THC, however a hair test may be able to show the gradual fall in concentration since the last dose. Just doing a hair test will still give a positive reading because there was THC in her body still while the hair grew if that makes any sense. the hair needs to be looked at in sections and assayed quantitatively. As I say though, a quantitative test that gives a numerical rather than -/+ or low/med/high could show the downward trend. Standard drug tests use an ELISA method though which is semi-quantative at best. You wo
