Toxicology question !!!?

Question

When someone has been on drugs, which are no longer detectible in his system, is there anything else in their toxicoogy screen that could suggest they were -not long ago- on drugs ? Please , it's very important, I'm not on drugs, I'm just working on a novel and it's a very important part of the story ! Thanks

Answer 1

Even though it is no longer in the system a person would still test positive on a hair test for a very long time.  For example, the component that lasts the longest in a tox screen is THC.  Even after a person tests negative in the urine for THC, the hair will still test positive until it grows out and cut off or sheds out.  If the drug was in the system when the hair was formed it will be there until you remove the hair.