I experimented with ecstasy, cocaine and marijuana..i am currently going to school to get my BS and havent touched any drugs recently. If i stay completely clean and sober for the next 3 years do you think i will have a chance of becoming an ivestigator or detective in the future?

My department would not hire you.

It will depends on the dept. Standards differ from dept. to dept. It could also depend on what you mean by "experimented with". How much, how many times, etc.

Having been clean for only 3 years won't be long enough for most departments