Gaspen Payne is a prosecutor from the Ace Attorney series. He was a district prosecutor in Los Angeles, before becoming the Chief Prosecutor of the Kingdom of Khura'in. He is the younger brother of Winston Payne, whose multiple defeats at the hands of Phoenix Wright prompted Gaspen to wish to defeat the renowed defense attorney himself. However, Phoenix Wright went on to beat him in both of their trials, only causing him humiliation.
Unlike his brother who generally plays by the rules, Gaspen in an unpleasant and corrupt man, who berates defendants, and uses underhanded tactics to win cases. This underhandedness extended to flat out villainy however when he tried to get the 9 year old child Ahlbi Ur'gaid executed. On top of this he tried to outright murder Phoenix Wright buy luring him towards getting unjustly executed under the "defense culpability act".
The Bombing Trial
Gaspen prosecuted the case of the courtroom bombing against Juniper Woods, whom he constantly berated and badgered, much to the anger of Athena Cykes. He successfully backed the aforementioned female attorney into a corner from the outset when he presented conclusive evidence, however Phoenix Wright arrived and took over the lead on the defense. Gaspen was thrilled to have a chance to defeat the attorney who had humiliated his younger brother, Winston Payne, so many times. However unfortunately for him, Phoenix was able to successfully prove Juniper innocent, proving the bomb disposal specialist Ted Tonate to be the true culprit. When Tonate threatened to detonate a supposed bomb he had on him, Gaspen fleed the courtroom in fear along with the citizens in the gallery. In his absence, Phoenix fearlessly provided proof that Tonate was bluffing, and the latter confessed to all his crimes, resulting in Juniper's not guilty verdict.
Ahlbi Ur'gaid's Trial
When Chief Prosecutor Edgeworth began to make progress on rooting out corruption within the prosecutor's office, Gaspen was one of the prosecutors that was chased out. He left the country and moved to Khura'in, a country which's legal system is devoid of attorneys and full of twisted corruption. He soon worked his way up the ranks, becoming the kingdom's chief prosecutor.
He prosecuted the case against the child Ahlbi Ur'gaid, who was charged with the theft of a sacred relic and the murder of a guard. However Phoenix Wright had coincidentally traveled to the country to visit a friend, and had interrupted the trial protesting, sticking up for Ahlbi's innocence. The Judge was going to throw the attorney out after explaining that Khura'in didn't have defence attorneys, but Gaspen saw an opportunity for revenge using the "DC Act" and so convinced the judge to allow him to defend the accused. Phoenix obliviously went along with it, not knowing about the DC Act until he was eventually informed by the judge that it meant if Ahlbi was found guilty, he'll also receive whatever punishment Ahlbi receives. It's at this moment that Gaspen pushes for the death penalty.
Despite this, Phoenix was able to prove Ahlbi's innocence, and proved Pees'lubn Andistan'dhin was the true culprit.