The police officer was reported that he used mixers to split the stolen bitcoin into smaller amounts, transferring the coins through crypto exchanges and prepaid cards to block the trace, but at last he was known.

https://cointelegraph.com/explained/how-a-police-officer-stole-50-btc-from-a-seized-crypto-wallet-and-got-caught

Some people may not know that bitcoin can be traced to someone if the government wants to trace it. This is not the first time such bad actors are known.