Harris is a Dominion administrative assistant who worked for Colonel Garr.
When Garr was reviewing Project Tamed, Harris arranged and scheduled a conference between Garr, Dr. Sandra Loew, and Emperor Arcturus Mengsk. After the emperor gave his approval to the project, Garr ordered Harris to send him files on the planet Thys.
References
Maxwell, Matthew. "The Teacher." (February 20, 2013). Blizzard Entertainment. The Teacher Accessed 2013-02-21.