He began working for the LAPD in 1981, and was set to retire in October of 2006. However he was having marital and financial problems. He was having an affair with Jessie Templeton. He was aware that Bosch was pursuing the unsolved case of Marie Gesto, and that Anthony Garland was the prime suspect. At the same time, he was aware that Raynard Waits was about to confess to a series of murders of young women. He approached Garland's father and his lawyer with a plan to pin the Gesto murder on Waits, in exchange for a large amount of money to fund his retirement. As part of this plan, he entered a false note into the file for Gesto to indicate that Robert Saxon had called Jerry Edgar claiming to be a witness.
Pratt's plan fell apart when it was uncovered by Bosch. Pratt then agreed to cooperate in a sting to catch Garland by demanding more money. Instead, Garland shot and killed Pratt.