David Turner and Toby Whitewood were a man and a teenager who embarked on a series of murders. They appeared in The Apprenticeship.
David and Toby decide to evolve from their killings of dogs to attacking prostitutes. Toby takes a bus to the city and asks for the services of a prostitute. While she is counting the money, he blitz-attacks and suffocates her, enjoying his first human kill. The next morning, he learns David was watching him when his tutor sends him a video of the act. He watches the video, excited. At his job, Toby sees David at the pet shop and asks to leave early. He meets with David, who criticizes his sloppiness. Toby apologizes, and David reassures him, after which he kills another prostitute as a lecture. Later, the two pick up another victim on the road and mutually kill her. Pleased with Toby's progress, David takes him to a hardware store to buy murder supplies, advising him what to buy and what not to use, like the difference between a simple garden hammer found almost everywhere, and a more efficient titanium one. This causes Toby to be late for his job, and his boss Hollie Riggio fires him. Enraged, Toby abducts her and brings her to David's house, expecting him to be pleased.
However, upon finding out, David angrily yells at Toby for not only abducting someone he knew, in his neighborhood, but also transporting her with her own car, and with the FBI in town. David takes Toby and Hollie to the boat dock owned by his father Nate, intending to dump Hollie in the water and clean up Toby's mess. The two get into an argument about who gets to kill Hollie, during which Toby accuses David of looking at him funny. Then, an angered Toby knocks David out with a hammer. Thinking he is dead, Toby tortures and taunts Hollie before being interrupted by David, who strangles him to death with his bare hands in a fit of rage. In shock after murdering his pupil, David rambles to Hollie before moving to kill her with a large tool, but is interrupted by the arrival of the BAU. Not wanting to go back to prison, David charges forward with the tool in hand and is shot and killed by Morgan. Later, in Carbon Copy, someone murders a woman using the duo's M.O. The duo was then mentioned in The Gathering.
Based on the victim type and kill-zone dynamics, the unsubs are two white males, one significantly older than the other. The younger unsub is an adolescent who probably lives in the area and is likely a student at a local high school. The older unsub is in his late 30s to early 40s who is sophisticated, so he probably has a violent criminal experience. He is most likely an ex-convict, but someone with law enforcement training cannot be ruled out. The older unsub has some sort of access to teenagers, but somehow, he does not stick out. He most likely lives or works in an area where young people would frequent, like a school, church, or community center. He is also charismatic and likely holds a job that would easily gain the trust of a teenager, such as a teacher or a coach. There is also a chance that they are related, possibly like a father and son, brothers, or maybe even an uncle and nephew.
The unsubs' relationship is a mentor-student type, in which the older one is trying to teach the younger one on how to be a better killer. This kind of killer team dynamic is rare, but this symbiotic nature of their mutual desires is what actually strengthens their affinity for one another. However, even if there is no biological connection, this relationship has all of the hallmarks of this kind of bond, especially if the younger unsub might be looking for a father figure and/or looking to fill in some kind of emotional void. Their killing pace is relentless, and given their combined appetites and this player-coach dynamic, these two are exceptionally dangerous.
Aspects of Turner and Whitewood's M.O. is similar to those of Peter Sutcliffe, who also targeted prostitutes, solicited them as a ruse, and used hammers on them; and Robert Lee Yates, who also targeted prostitutes, solicited them as a ruse, and left plastic bags on their heads after killing them as a signature.
David and Toby's relationship seems to have been based on the existing one between Dean Corll and his second accomplice, Elmer Wayne Hendley. In both cases, an experienced, ephebophilic, and homosexual killer in his 30s (Corll and David, though David may have been bisexual instead) mentored a fifteen-year-old boy, whom they were sexually attracted to (Henley and Toby, respectively), in serial killing, and used them to lure new victims for themselves. Subsequently, in both partnerships, the boy disobeyed the adult's advice and brought a victim that didn't fit the preferences of the adult, causing a confrontation and the eventual murder of one member by the other (though it was the adult who died in Corll and Henley's case, and the boy in David and Toby's). Also, like Corll, David revealed that he had plans to murder both the chosen victim and his own pupil, and was willing to be shot when someone pointed a gun at him and demanded that he release the victim. In addition, the confrontation between David and Toby took place in a boat shed, while Corll and Henley buried most of their mutual victims in one.
- November 5: Amanda Lopez (beaten, then fatally suffocated by Toby)
- November 6: Vicky Thomas (bit repeatedly and bludgeoned with a hammer by David)
- November 6-7: Shawna Radford (killed by both; tortured with suffocation and fatally bludgeoned with a hammer)
- November 7: Hollie Riggio (abducted and attempted to kill; was rescued)