Prosecutors sought a sentence of nine to 11 years because of the seriousness of the attack on Zehm, and its impact on the community.
"When officers abuse their power and lie to cover it up, it fundamentally undermines" their position of trust in the community, said Victor Boutros, a Justice Department attorney who helped prosecute the case.
On March 18, 2006, police received a report that a man matching Zehm's description might have stolen money from people at an ATM. Surveillance video showed that Thompson found Zehm inside a convenience store and immediately struck him repeatedly with a baton and shocked him with a stun gun.
Other officers arrived and hogtied Zehm, put a rubber mask over his mouth, and sat on him. It was later determined that he had not committed any crime.
His last words were: "All I wanted was a Snickers bar," according to trial testimony.
Anger boiled in the community over the death, but the Spokane County prosecutor's office declined to bring charges against any officers. Amid demands for justice, federal prosecutors eventually charged Thompson with violating Zehm's civil rights through use of excessive force and then lying to investigators.
Prosecutors also alleged the case involved an extensive cover-up by police. That investigation is ongoing.
Boutros said it was important to remember that Zehm, a mentally ill janitor, had committed no crime.
"He was just going in as he always did to buy his soda and his candy," Boutros said. Thompson's actions warranted prison time, he said.
"A badge cannot equate to a free pass," Boutros said.