This list covers all minor criminals mentioned in Season Three.
Mr. and Mrs. Laybourne
A couple that was the first set of murder victims of serial killer Gary. They were killed during a home invasion committed by Gary and his partner and former foster brother Ervin Robles, during which they both noticed they were abusing their daughter regularly. This triggered Gary to commit their murders, since it reminded him of the abuse he suffered at the hands of his foster parents.
Mr. and Mrs. Manwaring
A foster couple (an unnamed woman and her husband Hal) who abused the children under their care using a variety of methods. Mrs. Manwaring committed much of the abuse, while her husband turned a blind eye on it. Among the victims were Gary and Ervin, whose murders were sparked by the abuse. Gary would later try to have their current foster son kill them, but this ploy failed. They were presumably arrested immediately afterwards.
Jessica Davis's killer
Jessica Davis's murder, which predated the episode by one week, was initially thought to be connected to the case at hand. She was abducted from a mall and found dead hours later. According to Reid, the murderer, who remains unidentified and at large by the end of the episode, killed her because he realized that he could never have any privacy with her. News coverage of the murder would later be responsible for launching the prominent case.
The Scarsdale Skinner
The Scarsdale Skinner (real name unrevealed) was a serial killer operating in Scarsdale, New York. According to Reid, Rossi somehow helped capture him by using psycho-linguistics to profile his reading habits. Judging by the nickname, it can be assumed he flayed his victims.
The McCrellan Corporation
A predominantly Irish mob centered in Boston, which Jack Vaughan once worked as an enforcer for. The organization was particularly ruthless in regards to those it viewed as a threat, so any potential witnesses to their crimes never come forward for fear of retribution. The "corporation" may have been disbanded by the testimony of Jack, who had turned against the group and was placed in witness protection after his wife died in an attack that was meant for him. In the Season Twelve episode Green Light, it was revealed that Jack and his daughter Lindsey were eventually let go from witness protection, presumably because the McCrellan Corporation was dismantled for good.
The Indianapolis rapist
A serial rapist caught by Rossi in 1988. By his account, it was pretty easy as he wasn't very smart. After the case, Rossi was brought in on the murders of Mr. and Mrs. Galen.