Gary Mitchell was a 23rd century Human. Born on stardate 1087.7 in the city of Eldman, he later served as a Starfleet officer.
A medical study into Gary Mitchell's family history found that several members of his immediate family, and distant ancestors going back six generations on his mother's side, had esper-oriented abilities. One of his ancestors had an interest in "spiritual readings." His esper rating (091), aperception quotient (20/104), Duke-Heidelburg quotient (261), and general knowledge quotient (679532-112) were well above average in all categories.
Growing up, it was found he displayed unusual skill at "guessing games" – performing much better than chance would allow. He also had a grade school interest in magic tricks.