The sequencing itself was conducted under clean-room conditions—sterile environments designed to minimize the contamination of ancient or historical samples with modern DNA from researchers, from the environment, or from other samples. Modern human DNA contamination is one of the most persistent challenges in historical and ancient genomics; even tiny amounts of contamination can distort findings if not carefully controlled.
The authentication of the five matching locks was, in part, a quality-control mechanism for contamination. If contamination were a significant problem with any of the samples, the contaminated sample would likely show a different genetic profile from the others. The fact that five independent samples from different collections, stored differently and handled by different researchers over time, all showed matching profiles provided strong evidence that the results reflected the actual genetics of the individual whose hair they contained.
The Hiller Lock, which did not match, was not an example of contamination in this sense—it showed its own consistent genetic profile, that of a female with Ashkenazi Jewish ancestry. This was a coherent result, just not the result that had been expected. The lock was not randomly contaminated; it appeared to contain hair from a specific individual who was simply not Beethoven.
The technical achievement of the 2023 study was substantial: they recovered a nearly complete genome from nineteenth-century hair, authenticated it across multiple independent samples from different institutional sources, and extracted from it meaningful medical and genealogical information. The methodology represents an advance that will be applicable to other historical figures whose biological material has been preserved in museums, archives, and private collections around the world.