Is there a window for finding drugs?

Forensic toxicologist Lorna Nisbet gives us a glimpse as to how fast she has to work...

Lorna - Well, that depends on how the body breaks it down. So it's called something called the half life, and that's just basically the time it takes for half of the drug to get out of your body. And that's dependent on a whole lot of different things and lots of different biological and physiological models. But some are obviously extremely quick to get out of your system, like GHB, and others are really, really long lasting. So arsenic for example, you can exhume people and you can still find that in their body. It also depends on what you're actually testing people for. Things like your bloodstream: a lot of your drugs will come out of that relatively quickly. But your hair is constantly growing and as your blood is circulating around, as your hair grows, it incorporates some of that drug into your hair. So theoretically you should be able to get a timeline of somebody's drug abuse by taking hair. But it isn't a strand of hair, it's a full pencil just to get that mess away.