- "I was angry with her, really angry, I could have done it. Was it me?"
- ―James Tiernan
Tiernan works as a pin-setter and general mechanic at Rawling's Bowling Alley. Tiernan spent some of his time at the public library where he met and befriended Evelyn Summers. The two later would drink together, and even become lovers. Through Evelyn, Tiernan reluctantly became affiliated with Grosvenor McCaffrey, who Evelyn admired. However, McCaffrey loathed both Evelyn and Tiernan, a feeling that was at least mutual for Tiernan, creating a strange love and hate triangle.
While drinking together, Tiernan and Evelyn had an argument over their opposing feelings towards McCaffrey. Evelyn later returned with a quart of whiskey as a make-up gift. However, Tiernan rejected her and threw her out of his hotel room. Upset and angry over the fight, a drunken Tiernan went out to look for Evelyn, but was unable to find her. He woke up the next morning in McCaffery's apartment, with little to no memory of what happened. McCaffrey revealed to Tiernan that he (Tiernan) had in fact murdered Evelyn, but promised to protect him from the authorities and would dispose of the evidence. In actuality, McCaffrey was being framed for the murder by the Black Dahlia killer, prompting McCaffrey to use Tiernan as a scapegoat to protect himself.
Events of L.A. Noire
While working at the bowling alley, Detectives Cole Phelps and Rusty Galloway arrived to question him. However, he ran away in fear, as he was the last one to see Evelyn, and feared he would be charged. Tiernan was arrested after a car chase and taken to Central Police Station. With evidence pointing towards him as well as McCaffrey's accusation, along with his lack of personal recollection from being extremely drunk, Tiernan began to see the possibility of him being Evelyn's killer, tearfully assuming that he was the murderer. However, McCaffrey was charged, and Tiernan was released. However, neither McCaffrey or Tiernan were responsible for the murder, as the true killer was later revealed.
- The player has option of charging either Tiernan or McCaffrey. Charging Tiernan will result in a maximum three star case rating and a berating from Donnelly, who wanted McCaffery charged, but is biased by his own alliances, referring to him as a "Red".
- Tiernan is loosely based on the real-life James Tiernan, who did work at a bowling alley and was charged with the murder of Evelyn Winters, who Evelyn Summers was based upon.