At about eight and a half minutes into the episode, Avi and Van Miller are sitting at a diner counter. They both order coffee. Avi drugs his cup and then carefully adds sweetener and cream and stirs it in keeping with the way Van Miller is fixing his coffee. Avi then distracts Van Miller and switches their coffee cups. The switch is seen from above so the contents of the cups can easily be seen; both are black coffee - no cream.
Avi cuts about an inch of Agent Miller's hair and Ray tells Smith "That will test positive for LSD for about six years". Avi cut the end of Miller's hair leaving about two inches between the cut and the scalp, thus no way that any trace of LSD would be in the hair after only a few hours.