I could be wrong, but I don’t think that photographing a crime is a crime itself, unless you are photographing yourself commiting a crime.
I recently raised a similar question to a photo editor. I was present during a misdemeanor, and the police wanted to look through my pictures to see if I captured the culprit. The answer I got was to give the police my name and contact information, tell them I am a freelance photojournalist working on an assignment. If they wanted to have my pictures subpoenaed, after my attorney reviewed the paperwork, I would be happy to turn over copies of relevant photographs if there were any. If the crime were a murder or rape, etc., I would have been perfectly in my rights to help the police as I could, getting a subpoena after the fact to protect me.
I could be speaking out of turn, but it would seem that your drug story, although a little more complicated, can follow along the same path. You are pretty protected as a working photojournalist. If the police want your pictures, they have to subpoena them. Depending on the crime you witnessed/photographed, you can use your conscience on how proactive you want to be.
Just my 2Â¢. I’m sure others will have a more exacting answer.