John Clemens was a researcher initially belonging to the Chicago branch of the Umbrella Corporation.
History
Clemens was initially a member of the American research team at the Chicago Laboratory. In 1994, he was appointed as the replacement of former chief researcher William Birkin and transferred to the Arklay Laboratory, where he assisted in B.O.W. research and the development and the eventual completion of the t-virus. However, he had personal reservations about the research being conducted and saw it as overly cruel. Due to this, he was greatly disliked among the higher ups at Umbrella Headquarters who ignored and silenced his detractions. 1
At some point, Clemens entered into a relationship with Ada Wong, who had infiltrated the laboratory posing as a researcher in order to gather information on the t-virus. While Ada was actually a spy for a rival company, Clemens believed her to the very end. He also used her name as his personal password.
Following the outbreak of the t-virus at the facility in May 1998, John found that he himself was infected and promptly wrote a letter addressed to Ada, asking her to activate the facility's self-destruct sequence and expose Umbrella's deeds. 2 Instead, his zombified body and letter were found by S.T.A.R.S., Ada had already escaped the facility.