Drug Use: An item in the background investigation that really hurts many applicants is one I get questions about a lot, past drug use. First, let me say again each department may be a little different but most are along the same lines. Hard Drugs used even in the last 20 years is a disqualification most of the time, heroin, speed, LSD, addiction to prescription drugs are a few automatics for most police departments. Most agencies will not touch you if you were dealing drugs at all (that is a felony in case you did not realize it).
I actually had a kid ask me if he was disqualified if he had dealt pot back when he was a teenager (7 years ago), he just admitted to a felony, so of course you can guess the answer. Most agencies will not process you if you used drugs within the last 3 years. If you are five or more years out, it depends on what it was and how often. Daily as well as weekly usage is a sign of an addictive personality and the applicant may not be suitable for employment.