Comment by wildzzz

The only 100% safe method is to not do the illegal activity at all. There's always a risk/rewards analysis to be performed when committing any act that could have negative consequences whether you're playing the stock market or doing credit card fraud. For any major criminal that gets caught, you can usually read the arrest affidavit which offers a pretty interesting look into how the criminal was caught despite the careful measures they took. The one for DPR is interesting to read and shows how despite taking careful measures, DPR left a trail of breadcrumbs that investigators used to track him down. His use of Tor was pretty solid (assuming the whole affidavit isn't complete parallel construction fiction) but it was everything else he did outside of it that got him in the end. There's another story of a university student that sent threats to his school to get out of an exam or something through anonymous emails over Tor. They only caught him because he was the only person using Tor on the school network at the time the email was sent. If he was off campus, he may have remained anonymous.

An analog crime I think about is the murders in Moscow, Idaho. The criminal did take some careful measures like wearing gloves but he left a knife sheath behind that contained DNA evidence. Everything else they had on him was circumstantial, he owned a similar car to what police thought they saw on people's doorbell cameras and his phone went offline during the time of the murders and also pinged a tower close to the crime scene hours afterwards. Police found a partial genealogy match to his DNA which I'm sure they compared to similar car owners and cell tower records. If he hadn't left the sheath behind, wore something like a Tyvek suit, and simply left his phone at home, the suspect pool would have likely been too large. His careful measures (turning off his phone, making multiple passes in his car) likely contributed to police focusing on him once the DNA proved a link.