James "Jimmy" McNulty is a member of the UTA Marines' Sigma Squad and Ezra Mason's friend.
James McNulty is described as a man who would've been a good father.
James McNulty is first introduced as Ezra Mason's friend.
As the story progresses, he is sent on a mission with the Sigma Squad. He is supposed to terminate the evacuees in Hangar Bay 4 which survived the attack on the Copernicus. The evacuees, however, are infected with the Phobos Virus, making them extremely violent. In an attempt to save a little girl, one of his teammates' throat is sliced open and his own suit is damaged. After trying to escape with the rest of his crew, the higher in commands order that he is not allowed to exit Hangar Bay 4 as he was exposed to the virus. Understanding his situation, Jimmy decides to stay behind Airlock 2, while the rest of his team evacuates.
- He was the one who gave Kady the nickname "Astro-Princess".