Corporal Pettigrew was a member of the United States Colonial Marine Corps. He was a member of the USCM security detail stationed at Hadley's Hope on Acheron in 2179. He was subsequently involved in combating the Xenomorph infestation at the colony.
Pettigrew was part of a small group of disruptive Marines at the colony, led by Sergeant Marvin Draper, who were in conflict with their new commanding officer, Captain Demian Brackett. He was killed by a Xenomorph as he and the few surviving Marines attempted to escape the planet aboard the hidden Weyland-Yutani ship.
- In the novel Alien: River of Pain, Pettigrew is male, yet in the audio drama adaptation she is female (voiced by actress Karen Bartke).