Joe Darke was a businessman who killed several people in 2015 in an incident known as the SL-9 Incident in police files. He was wrongfully convicted and executed for the murder of Neil Marshall, the only one of the incidents' victims that he did not kill, via falsified evidence. Marshall's real killer would not be arrested for another two years.
- Main article: SL-9 Incident
In 2015, the Criminal Affairs Department had a special team investigate the spree killings of Edward Jones, Jason Knight, Edith Kirby, Rachael Moss, and Jeb Bates. The team's working hypothesis was that, on his way home from work, Joe Darke had accidentally hit a man with his car, killing him. Events had then quickly spiraled out of control as Darke murdered a man who had witnessed the accident, followed by a lady who had witnessed this second crime, and then a child who had been walking by the crime scene at the time. A jogger had also stumbled across Darke as the latter was burying the bodies and was killed as well. However, this was all conjecture with no decisive evidence, until Darke turned himself in.
Criminal Affairs Deputy Chief Damon Gant and Prosecutor Neil Marshall interrogated Darke. However, during questioning a thunderstorm blew out the power, allowing the suspect to escape. He ran into the shared office of Gant and Detective Lana Skye, where he found Lana's younger sister, Ema. When Marshall arrived, Darke held Ema hostage and threatened to kill her. In the ensuing struggle, Marshall knocked Darke unconscious with his recently earned King of Prosecutors Trophy. When Darke woke up, Marshall was impaled on a suit of armor, and he was arrested for the murder.
- Main article: Rise from the Ashes
Joe Darke was put on trial, with Miles Edgeworth prosecuting his case. The trial ended with Darke being found guilty, sentenced to death, and executed. Soon afterward, however, detectives Jake Marshall (Neil's brother) and Angel Starr, who had worked on Darke's case, were demoted and fired, respectively, and Gant and Lana were promoted to Chief of Police and Chief Prosecutor, respectively. This led to lingering questions and suspicion by Jake and Starr.
Two years later, Detective Bruce Goodman was murdered and Lana was put on trial for the deed. The truth behind Darke's conviction began to unravel as defense attorney Phoenix Wright and prosecutor Edgeworth argued in court, and it was soon revealed that Gant had murdered both Goodman and Neil. Partially motivated by the lack of decisive evidence that could convict Darke, Gant had murdered Neil and tampered with the crime scene to convince Lana that Ema had been responsible for the crime. Through this, he had been able to control both the police department and the prosecutor's office by blackmailing Lana. Two years after the murder, Jake had convinced Goodman to try to convince Gant to reopen the SL-9 case, causing the latter to murder him in a panic.
- The Japanese name "Aokage" means "pale shadow", likely in reference to his light hair and skin tone, as well as his sinister nature.
- The name "Darke" probably refers to Darke's frightening nature and the shadowy nature of the SL-9 Incident, making him a shadowy figure from the past.
- His initials are J.D., an abbreviation shared by "John Doe", a term used by detectives to describe an unknown person. The name "John Doe" would later be used as the cover name for Shelly de Killer.
- The French name "Sinister" also reflects the nature of the incident and of Darke himself.
- In the unofficial Brazilian translation his name is João Trevaz; João comes from the Hebrew Yehokhanan or Iohanan, which means "grandfathered by God"; Trevaz is an alternate spelling of the surname "Trevas" ("darkness"); It refers to the fact that he is a dark character.
- Darke is not encountered in-game, although he is an important part of the plot, akin to Ami Fey. He appears in the court record with his face obscured by shadow, but with unobscured features in flashbacks.