- In 2002, crime novelist Patricia Cornwell, in Portrait of a Killer: Jack the Ripper—Case Closed, maintained that Sickert was Jack the Ripper. A psychological motivation for Sickert was said to be a congenital anomaly of his penis. Cornwell purchased 31 of Sickert's paintings, and some in the art world have said that she destroyed one of them in a search for Sickert's DNA, but Cornwell denies having done this. Cornwell claimed she was able to scientifically prove that Mitochondrial DNA from one of more than 600 Ripper-letters sent to Scotland Yard and mitochondrial DNA from a letter written by Sickert belong to only one percent of the population.
In 2004, the Oxford Dictionary of National Biography, in its article on Sickert, dismissed any claim that he was Jack the Ripper as "fantasy".
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, adenosine triphosphate (ATP). Mitochondrial DNA is only a small portion of the DNA in a eukaryotic cell; most of the DNA can be found in the cell nucleus and, in plants and algae, also in the plastids, like chloroplasts.