Coming at this from a slightly different direction: what would be the issue with him taking literally any drug if he’s already in custody? Do they think there are ‘break out of jail’ pills? If he was literally just taking recreational drugs, wouldn’t that just give them an even clearer ‘probable cause’ to hold him? If they have no duty to enforce the law, they can’t be held responsible for letting it happen. If he takes cyanide and keels over, doesn’t that just do what the cops want and ‘take another criminal off the streets?’ They don’t care about his continued life or they’d be bringing in a doctor on first request. There is zero downside for the cops to just letting people take whatever they want.