William Birkin was an Umbrella scientist and Albert Weskers only genuine friend. He took credit for the creation of the tyrant virus upon the assasination of its creator, James Marcus.
He discovered the G-virus soon after and began researching into potential use as a Bio-weapon.
He was assassinated by the USSFU team under the command of HUNK, who mistook a sudden sound of a coffee mug hitting the floor as an attempt to kill them.
They escaped with the G-virus case, but did not notice Birkin inject a sample into his body after being shot.
The monster then took revenge on the team, spreading the tyrant virus in the process.
He was killed by an explosion triggered by his presence on an Umbrella-owned train.