Franklin Accardo was a former member of an infamous racketeering group imprisoned for twenty years at Blackgate known as the "Blüdhaven Six" six one of six victims to Professor Pyg's unethical experiments to eliminate physical imperfections.
Franklin Accardo had frequently been in jail since he was young, namely for drug charges, and also possessed juvenile arthritis, a rare and debilitating condition, resulting in his left knee getting bone deformation. At some point, he ended up joining an infamous racketeering group known as the Blüdhaven six, having the burn mark on his upper left arm to prove it. Eventually, he ended up caught, and was sentenced to twenty years at Blackgate alongside the rest of his group. He was eventually released early due to a debilitating heart condition that also necessitated a pace-maker to be implanted into him. He later moved to Little Rock, Arkansas.
Some time later, the Circus of the Strange travelled to Little Rock, Arkansas, with Franklin Accardo being abducted during this time, also resulting in his being taken back to Gotham City to be experimented on by the group's leader, Professor Pyg. However, his physical defects were such that even Pyg couldn't fix them, so Pyg killed him by overdosing him on pain-killers, as well as doused his fingers into acid to remove fingerprints and thus any remaining DNA that wasn't corrupted from the Dollatron experiments. He was then hung at the top of a building on Bleake Island with the word "Failure" written to the side of it and opera music playing nearby.
Batman later found his corpse while conducting an investigation on the bodies. Because he couldn't directly ID the victim by DNA analysis both due to the acid eliminating fingerprints and his overall DNA being corrupted, he instead used several clues in various parts of his body to come up with a match with any people who were declared missing.