As a young man Lonnie joined the Sparta Police Department, working for Chief Bill Gillespie. Like many of the others in the department Lonnie wasn't exactly thrilled about the arrival of Virgil Tibbs, but soon became friends with Virgil and his wife Althea. He was also friends with many of the other officers in the department, such as Bubba Skinner and Parker Williams.
On duty Lonnie had a straightforward, no nonsense personality. He was an excellent sharpshooter and Chief Gillespie would often turn to him when he needed a long range rifle shot. Between Lonnie and Bubba Skinner the Sparta PD had a lethal sniper team.
In his off hours Lonnie volunteered as a track coach at the local high school and took care of his Corvette. Lonnie was generally a friendly and approachable person who was very loyal to his friends.
In 1994 a number of changes came to the Sparta PD as Tibbs left to begin a new career as an attorney. Additionally Bill Gillespie was terminated by the city council and replaced by the former Memphis police investigator Hampton Forbes. Jamison remained with the department, having achieved the rank of Lieutenant and being named Acting Chief of Detectives.