It depends on what state you are in and the circumstance involving the crime.
They take all drugs back for lab testing these days to find out the exact weight of the active illegal chemical you were caught with so they have a stronger case against the alleged person.
In saying that though; if you were caught with 5 MDMA pills, several clippy bags and a stack of cash, they would have grounds enough to charge you with trafficking and you would want to get your affairs in order with a good lawyer. Even if they found no drugs but found lots of money, clippy bags, and scales but, on the scales they found drug traces then they may be able to build a case against you, it just depends on whether they really wanted you or not.
With LSD though, 10 or over is getting a bit risky and they will try to get you with trafficking charges. If you're not dealing though and are caught with nothing more than that, the charge will usually get thrown out at court and you will just receive a possession charge....
Hope this has been a little bit of help to you :D