- "I hear you're a good case man, but if you fuck up on my detail I'll have you out of here before your feet touch the ground."
- ―Lachlan McKelty to Cole Phelps
Events of L.A. Noire
McKelty wears a blue suit with a scarlet striped tie. He is first seen during Cole Phelps' first day on the arson desk, after he was demoted from vice. McKelty introduced Phelps to the other detectives, including William Tilden, who then verbally harassed Phelps regarding the scandal that landed him there. McKelty, however, told the detectives that he did not care about Cole's former actions, because Cole "a good case man". McKelty partnered Phelps with Herschel Biggs, and assigned him the arson case regarding two house fires. The case ended with the arrest of Matthew Ryan, a fifth columnist employee of InstaHeat, a result that pleased McKelty.
McKelty later assigned Phelps and Biggs to investigate the Morelli house fire. When Phelps became suspicious of Leland Monroe, McKelty angrily warned him to stop investigating Monroe, citing Monroe's prominence and high-level connections in the city's administration. Phelps continued his line of inquiry despite the warning, hence McKelty warned off Biggs by threatening to compromise his pension. When Phelps killed Herbert Chapman, a suspected arsonist and annoyance to the arson department, during the investigation McKelty expressed great relief, since he shared a strong dislike for him.
McKelty appeared again at the conclusion of Nicholson Electroplating. He praised Phelps and Biggs for solving the Nicholson Electroplating Plant explosion, while also killing Vernon Mapes, a corrupt former LAPD detective. He then states that Cole might have just made the case of the decade.
McKelty has shown to have an extremely short fuse and bad temper. His attitude likely stems from the fact that Arson is a lowly squad with few results, hence is highly intolerant of errors and failure. He does express satisfaction towards Phelps for arresting Matthew Ryan and for killing Herbert Chapman and Vernon Mapes, but withholds high praise due to Phelps' scandal. McKelty is also an honest cop, evident by his dislike for Vernon Mapes.