“And the death of a slave was not necessarily a crime.” That would be the murder of a slave by their owner, but certainly not by the patty rollers or any one else. The people hired for the slave patrol would be lower class, and quite possibly Irish immigrants, which is where the “patty” may come from. Irish immigrants frequently got dirty jobs that slaves couldn’t do like tunneling, draining swamps, or being an overseer. Many of the first cops in Northern cities were Irish too. In any case, if a slave was killed or seriously injured by the patrol they’d be responsible for the substantial value, or at least the lost work if the slave had to recover. The slaves owners had to pay a tax to fund the slave patrol to protect their property from disappearing, not to have them killed or maimed. A patty roller who was killing or beating slaves wouldn’t have that job very long.