Suspect killed in Thursday's shooting was shot by LMPD detective, Chief Conrad says

In other words, if the police aren't there and about to take the evidence, and totally miss it, then a defendant's legal team can do whatever they want with it. Flushing drugs down a toilet is tampering because the police would inevitably seize it as evidence. There were no police looking for those casings when his legal time found them, so they weren't required to do anything. They erred on the safe side and preserved them, I'm assuming because he was looking for a deal.