Joseph Barnett was born c. 1858 and raise less than a mile from the heart of Whitechapel. His father died in 1864, when Joe was six, and his mother abandoned the children soon after, leaving the eldest children to take care of themselves. By 1878 Joe and his three brothers were all working as fish porters at Billingsgate Market, a job which their father had held before them.
In April of 1887 he met Mary Jane Kelly for the first time, and the following day they decided to move in together. Much of what is known about Kelly was told by Barnett to police after her death. In 1888 they took a room together at 13 Miller's Court. In July of 1888 Barnett lost his job a Billingsgate, ostensibly because he was caught stealing. On October 30th he and Kelly quarreled, and he left the room they shared. He claimed that this fight was because a prostitute, known to him only by the name Julia, was sharing the room at the time. It was probably at this time that the window next to the door was broken. After this fight he took lodgings in Bishopsgate, but continued to visit Kelly between the 1st and the 8th of November, sometimes giving her money. He left her room for the last time at 8 p.m. on November 8th. Her body was found mutilated in the room at 10:45 the next morning.
After the murder Barnett was interrogated for four hours, after which the police seemed satisfied that he was not the killer. It was not suggested that he was a suspect again until almost a century later, when author Bruce Paley first suggested that Barnett was jealous of Kelly and committed the other four murders in the hopes of scaring her out of prostitution, and when this failed, murdering her. Other suggest that he only killed Kelly and mutilated her in order to tie the crime in with Jack the Ripper, though of the two suggestions this seems the less likely. Though Barnett does seem to have similarities to some of the descriptions of the killer, and matches some aspects of the profile created by the FBI a century after the crimes, it must be remembered that Barnett was exonerated by contemporary investigation, and appears to have had an alibi for the night of Kelly's murder.