Clemens worked in the 1980s as a researcher at Umbrella USA's Chicago headquarters. Some time between 1991 and 1995, Clemens was transferred to the Arklay Laboratory outside Raccoon City, where he was to take over Dr. William Birkin's role as chief of research. While a brilliant scientist, Clemens did not have the stomach for Umbrella's illegal weapons research, which Umbrella considered a negative personality trait. A rumour among Umbrella Intelligence Division operatives was that in the event of an information leak he would be the primary suspect. Around 1998, a rival company infiltrated Umbrella USA and planted Ada Wong as a researcher to send back information. Wong and Clemens built up a relationship, which Clemens was serious about and was well known to other members of staff. When the t-Virus escaped containment, Clemens was infected, and in his last moments wrote a letter to Ada giving information on how to activate the facility's self-destruct system, and telling her to take evidence of Umbrella's experiments and expose them to the public. She never read the letter.
In S.D. Perry's novelization of Resident Evil, John is given the surname "Howe". It should be noted that the S.D. Perry novels have their own separate canon outside of the games, and should not be used as fact when referring to characters in the games.
↑Resident Evil 2 (1998), dialogue: Annette Birkin: "Ada Wong? I've heard that name before. Now I remember. One of the men from Chicago who came to assist the t-Virus research used his girlfriend's name as his password. 'Ada' and 'John', I believe."