Iain McGregor Hamilton was born in Paisley, Scotland in 1950. His parents immigrated to the United States and they settled in Burbank, California in 1953. After graduating from Verdugo Hills High School in 1968, he attended Los Angeles Valley College for two years before transferring to UCLA and graduating with a BA in Political Science, with an emphasis in International Relations, in 1972. He later received an MA in Public Relations from Pepperdine University and a second BA in history from California State University, Northridge.

He began his police career in March 1973 when he entered the Los Angeles Police Academy for six months of training. He was assigned to Foothill Division as part of his fifth month training requirement, and then initially assigned to Hollywood Division upon Police Academy graduation. After he completed his six month probation period, he was assigned to Communications Division, before being transferred to West Valley Division. While at West Valley Division he was assigned to patrol, a detective unit, and the West Valley jail. He worked for a period in the Van Nuys Division, before returning to West Valley Division, where he remained until his retirement in September 2005.