I have a story involving a town in the late 90s where vampires, among other mythical humanoids, openly live amongst humans. These vampires are the friendly, pro-human sort, and thus they have a lot of rules in place to prevent vampires from abusing their inherent position of power over their human neighbors. One specific rule is in regards to vampires' ability to control minds.
All vampires have the power to send humans into a dazed, sleepy state in which they won't consciously remember anything or feel pain for a few minutes, and this is how they secure blood when they don't have willing donors. However, more powerful vampires have the ability to outright control minds, giving humans orders they have to follow, making them truthfully answer any question, and making them accept anything the vampire says as an objective fact. Skilled vampires can deliver pretty intricate instructions that can even alter a human's personality or perception entirely.
This is obviously absurdly open to abuse to commit some grotesque crimes (not to mention turn any human into a potential unwilling mole for enemy clans of vampires and the like), so the town has a countermeasure set up: they figured out a few centuries ago that strongly pushing a certain pressure point on a human's back while they're in a trance will not only snap them out of that trance, but undo all mind control any vampire has applied to them and make them suddenly remember everything that happened to them while in a trance, including what the vampire told them to do.
So every week, a group of vampires checks in with every human in town, applies that pressure point, and sees if any vampire has been abusing their powers on unconsenting humans. If the human discovers in the process that they have in fact been controlled in any way without their knowledge (there are humans who willingly go under mind control for therapeutic or recreational purposes), they can then say so, and the group doing the check will put them under a trance to make sure they're telling the truth, and if so, severely punish the vampire in question.
Sounds good, except I discovered a pretty serious flaw with this system that I decided we're going to see in action as a plot point: this only works if the human is still alive to rat the vampire out at the end of the week. Meaning it's countered by, and in fact encourages, the murder of mind-controlled victims, either right after the fact, or with for example a hypnotic command to commit suicide at the end of the week.
After the latter happens, obviously the vampires are going to decide they need a better system. But I'm having trouble thinking of one that wouldn't be a massive nuisance or invasion of privacy for the humans of the town.
How can my vampire town most effectively discover, punish, and prevent abuse of their mind control powers on humans, all while respecting human rights as much as they can in the process?