Modern forensic techniques have put an end to a nearly 200-year-old conspiracy theory regarding a lost European prince, according to a new preprint paper.

In 1828, a "half-wild" 16-year-old boy took the continent by storm when he appeared seemingly out of nowhere in the German city of Nuremberg. The disheveled adolescent carried two letters on his person that claimed he had grown up in a dark and cold dungeon, held captive by a 'mystery man'.

The "feral child" couldn't speak well, but he wrote his name as Kaspar Hauser. Soon enough, rumors began to swirl as to where he came from.

Within a year, a popular hypothesis had emerged. Some claimed that Hauser was the son of the recently deceased Grand Duke Carl, who used to be a prince in Baden, a territory in south Germany, before the dissolution of the Holy Roman Empire in 1806.

History has it that the Grand Duke's only surviving son died as an infant in 1812. With the sudden appearance of Hauser, however, some began speculating that the House of Baden's real heir was kidnapped and swapped out with a dying baby "to bring a collateral lineage to the throne".

Five years after Hauser's mysterious appearance, the young man was stabbed to death, adding even more intrigue to his case and inspiring hundreds of articles, books, films, and plays over the decades.

"It's claimed to be one of the biggest historical mysteries of the 19th century," says geneticist Turi King, who was one of the researchers who helped identify King Richard III's skeleton in 2014, in a podcast.

A few years ago, King was asked to join an international team of scientists trying to match the hair and blood of Kaspar Hauser to descendants of the House of Baden once and for all.

Previous attempts to do this had produced inconsistent results, and some scientists disputed whether the bloodstains, taken from Hauser's underwear on the day he was stabbed, were truly authentic.

"After death, our DNA degrades into shorter and shorter fragments until there is nothing left to sequence," explains King, who currently works at the University of Bath.

"The DNA analysis methods available in the 1990s and early 2000s worked well with long DNA fragments, but didn't give consistent results when they did DNA analysis of the various items from Hauser."

Using samples of Hauser's blood and hair, King and her colleagues re-analyzed the young man's mitochondrial DNA, which is inherited via the maternal line, using modern sequencing techniques.

"The DNA from Kaspar Hauser was the same across the hair samples and also matched the blood sample analysis of 1990s," explains King. This confirms the authenticity of the samples for the first time.

When researchers compared Hauser's mtDNA to those of his supposed royal sisters and their descendants, however, there was no match.

The team concludes that Hauser's genes were "clearly different from the mitochondrial lineage of the House of Baden". As such, this "rules out a maternal relationship" and "the widely believed 'Prince Theory'."

"Sadly our data still can't tell us who he was!" says King.

"His mitochondrial DNA type is one that's Westeurasian, but we can't narrow it down to a geographical region."

Without royal blood, Hauser's origins remain a mystery. We may never know where this lost boy truly came from.

The study has been accepted for publication in iScience.