If my nephew smoked crack and snorted coke a liite less than a month ago would he pass a saliva test?

It depends on : How much he's used & for how long. The metabolites of Cocaine can be found in saliva for "an extended period" in chronic users; the higher the chronic doses, the longer the "extended period." a positive screen has medico-legal consequences including mandatory " rehab, " which may just save his life...Or, at least, prevent further damage to his body & brain. Help him focus on how to get healthy.

Cocaine: Yes, the half life of Cocaine is very short and it should all be out of his system. If he tests positive, then you know what.