Adam Donner is the former assistant district attorney of Starling City. He worked under Kate Spencer, the district attorney, and was Laurel Lance's ex-boss; he fired her for her drug addiction. He lost his job after being caught up in the hostage crisis at the courthouse, making it his fault.
In "City of Heroes",
In "Crucible", he takes Laurel out to dinner and makes romantic advances towards her, but she rebuffs him.
In "League of Assassins", he and Laurel meet with Moira and her lawyer to offer Moira a plea bargain which would allow her to avoid the death penalty.
In "State v. Queen", he serves as the lead prosecutor in the trial of Moira Queen. Before the trial begins, he informs Laurel that he has a "trump card" that will turn the jury against Moira. While cross-examining Thea Queen, he suddenly collapses in the courtroom, an unwitting victim of Count Vertigo's newest scheme to spread Vertigo throughout Starling City. He is then kidnapped by the Count, who forces him to beg, on a live TV broadcast, for another injection of Vertigo to ease his withdrawal symptoms. Later he is freed by The Arrow.
In "Blind Spot", he refuses Laurel's request to investigate Sebastian Blood, saying it would jeopardize his career. After Laurel is arrested for possession of drugs, he tells her that charges will not be filed, but fires her from the DA's office.
In "Birds of Prey", he reinstates Laurel as an ADA to be prosecutor against Frank Bertinelli. This turns out to be a ruse to lure out Helena Bertinelli so the police can capture her. It backfires, resulting in a hostage crisis at the courthouse. Kate Spencer states to Laurel that he did not have the authorization to rehire her, and that he lost his job as ADA, although Laurel is able to parlay her own knowledge of the trap and its disastrous consequences into still getting rehired herself.