If someone walks up to you and asks “hey, remember that time somebody used DNA evidence to identify Jack the Ripper?,” there are actually three completely different situations that person could be talking about. The most interesting and well-publicized came around last week when mitochondrial DNA matching longtime suspect Aaron Kosminski showed up on a shawl allegedly found at a Ripper crime scene, but DNA evidence also identified—or sort of identified—Jack the Ripper in 2004 and 2006. Each time, the evidence pointed to different people. And neither of them was Kosminski.

The first, artist Walter Sickert (1860-1942), was himself a Ripperologist of sorts whose paintings played with themes associated with the murders. In 2004, mystery novelist and true crime writer Patricia Cornwell, who has long believed Sickert committed the Ripper murders, claimed to have found his mitochondrial DNA on a letter ostensibly from the Ripper. There are three major problems with this theory:

1. The Ripper letters linked to Sickert’s mitochondrial DNA may not have been written by Jack the Ripper. Scotland Yard received countless letters purportedly from Jack the Ripper from the late 1880s on; none of them were proven to be genuine, and the vast majority were obvious hoaxes. Cornwell relied in part on mtDNA from the Openshaw letter, which is generally regarded as one of the likelier candidates, but that’s not necessarily saying much.
2. In addition to being over a century old, the letters were contaminated.
3. Even if the letters contain the author’s original mitochondrial DNA (and there is no way of knowing whether they do), 4% of the population shares the same mitochondrial DNA.

While Cornwell’s case against Sickert is not based entirely on the DNA, the DNA evidence is generally considered weak by Ripperologists today—though it could be argued that it’s about as strong as the DNA evidence in favor of Kosminski. Both rely, after all, on contaminated physical evidence that may or may not actually contain the Ripper’s DNA, and both rely on mitochondrial DNA matching that could eliminate 96% of suspects but does nothing to narrow the field among the remaining 4%.

Walter Sickert in 1911. Sickert was almost certainly innocent of the Ripper murders, but his own fascination with the case made him a suspect after his death.

The water was muddied further in 2006, when Australian geneticist Ian Findlay studied the same Openshaw letter Cornwell matched to Sickert and attempted to create a more comprehensive DNA profile than mitochondrial DNA alone would allow. His conclusion that the letter’s author may have been a woman should be taken with a grain of salt, for the same reasons mentioned above, but it did have the effect of further weakening the case against Sickert—and bringing new public attention to female Ripper suspects, of which there were relatively few.

Whether the case against Kosminski is weakened or strengthened by scrutiny, he is not the first suspect proven by DNA testing to be Jack the Ripper. He probably won’t be the last.