Jasper Sitwell graduated at the top of his class at S.H.I.E.L.D. Academy, with particularly high marks in airborne jump school and underwater maneuvers. Mentored by Nick Fury himself, Sitwell was occasionally appointed interim director when Fury is on solo missions in the field.
Major Story Arcs
Sitwell was later is assigned to Stark Industries as liaison them between S.H.I.E.L.D. There he confronts costumed assassins and terrorists such as Grey Gargoyle, Spymaster, A.I.M., and Madame Masque, with whom he became romantically involved. Sitwell was eventually reassigned back to S.H.I.E.L.D., but maintained his involvement with affairs of Tony Stark. When Obadiah Stane took over Stark International, Fury sent Sitwell to retrieve Stark's Iron Man armors, a mission which he ultimately failed.
Back at S.H.I.E.L.D.
Sitwell is seemingly killed by a self-aware, renegade Life Model Decoys, and replaced by one such LMD. However, the real Sitwell later turns up alive after having been brainwashed by HYDRA and placed in suspended animation as part of a plot against Fury; Sitwell is eventually deprogrammed. He has since become S.H.I.E.L.D.'s top interrogator, often paired with fellow agent, Jimmy Woo. He has also worked closely with G. W. Bridge, mainly in an attempt to neutralize the Punisher.
Sitwell was one of the many S.H.I.E.L.D. agents who refused to join Norman Osborn's H.A.M.M.E.R. organization in the wake of the Skrull Invasion, instead joining with Dum Dum Dugan to reform the Howling Commandos. The team engaged H.A.M.M.E.R., HYDRA, and Leviathan" program, alongside Nick Fury's Secret Warriors.
During one of the Winter Soldier's mission, a brainwashed Black Widow is brought into custody. When she tried to followed her programming and kill Nick Fury, Sitwell jumped in front of Fury, sacrificing his own life and saving Fury's.
Actor Maximiliano Hernández has portrayed Agent Sitwell in all of his Cinematic Universe appearances.
Sitwell was sent to New Mexico after Agent Phil Coulson found Mjölnir in the desert. He was among the S.H.I.E.L.D. agents who confiscated Jane Foster's research on wormholes. When another wormhole was opened in the desert, Sitwell, Coulson and some other agents went to the location and witnessed the arrival of The Destroyer. He asked Coulson if it is something of Stark's, but Coulson responded that Stark never told him anything.
Marvel One-Shot: The Consultant
Agent Sitwell summoned Agent Coulson to a meeting in a cafe to discuss a major problem: the World Security Council wanted Emil Blonsky freed from custody and integrated into The Avengers Initiative. Knowing the truth about the Abomination, the two of them decided to send the Consultant to annoy General Ross, to the point that he would never release his prisoner.
Sitwell was seen as a computer expert on the S.H.I.E.L.D Helicarrier and was the agent who located Loki in Stuttgart. During Hawkeye's attack on the ship, Sitwell's abilities were essential in regaining the control of the Helicarrier despite the heavy damages.
Marvel One-Shot: Item 47
Agent Sitwell was ordered to find and eliminate two bank robbers, Benny and Claire, who had obtained a functioning Chitauri gun. Anticipating the robbers' movements he found them in a motel, where he took the room next theirs and cranked up his music. When Benny knocked on Sitwell's door to ask him to lower the volume, Sitwell easily knocked him out and restrained him.
However, Benny managed to warn Claire, who began to attack Sitwell with the alien gun. During ensuing fight, the gun broke and started to shot automatically, destroying much of the room. Sitwell succeeded in securing Benny and Claire and prepared to follow his orders, until he discovered that the gun was only working because Benny had repaired it. Seeing a potential in the couple, Sitwell recruited Benny and Claire in S.H.I.E.L.D. instead of killing them.
Captain America: The Winter Soldier
Agent Sitwell was one of the hostages taken on the Lemurian Star by Georges Batroc and his fellow mercenaries. Batroc tried to ransom the hostages back to S.H.I.E.L.D., but before the negotiations were complete, Sitwell and the hostages were rescued by Captain America and a S.H.I.E.L.D. S.T.R.I.K.E. team.
Sitwell took an active role in the hunt of Captain America and his allies after Nick Fury's apparent death. When in the company of Stern, who are both revealed to be HYDRA agents, Sitwell was captured by Rogers, Romanoff, and Sam Wilson, looking for answers. Natasha threw Sitwell off of the roof to encourage him to talk, where Wilson grabbed him using a flight pack. Sitwell revealed to them that the new Helicarriers were programmed to kill individuals considered to be actual or potential threats to HYDRA, including Bruce Banner, President Ellis and Stephen Strange.
When Rogers and his allies attempted to return with Sitwell to the Triskelion and use him to access further information, the Winter Soldier attacked their vehicle and silenced Sitwell by throwing him in front of a passing truck.