David Groves, better known by his birth name Patrick David Mackay (born 25 September 1952), is a British serial killer who is believed to be one of the United Kingdom's most prolific serial murderers. He confessed to murdering thirteen people across London, Essex and Kent in England between 1973 and 1975. After retracting his confessions to nine of the killings, he was convicted of three counts of manslaughter; two additional cases were left to lie on file and police later found proof that he had killed one of these two victims. All of his confessions were found to match existing unsolved murders in and around London, and no one else has ever been arrested, charged or convicted for these officially still-unsolved crimes. He also attempted to kill a boy as a child.