Part of the reason it's impossible to tell just whether or not there's true elements to the story is that there's a few other serial killers that were running around at the time, including Peter Niers. His story is just as wild and contains some similar elements that many people (boring, cynical people) suggest is proof that you can't believe everything that you hear.
Executed Today says that Niers was definitely real, and that he was definitely a killer. The first mentions of him appear in 1577, when pamphlets telling the story of his capture were published and circulated. Niers first admitted to killing 75 people, but it's also worth mentioning that this confession came under torture. That wasn't the end of him, though — he reportedly broke out of jail and headed back out into the woods.
He wasn't recaptured again until 1581 — the same year Christman Genipperteinga reportedly met his end — and like Genipperteinga, Niers was executed via breaking on the wheel.
As if Niers' story wasn't terrible enough, it was also wildly embellished. Pamphlets from the era suggest that he had learned the art of invisibility, and by 1583, literature claimed that he had made a pact with the devil. In exchange for supernatural powers, Niers killed 544 people in the name of the devil. That included 24 pregnant women, the story went, and it was actually their unborn babies that Niers needed for his black magic rituals.
