Martin Frederick Cotton II, 26, was beaten by two officers in 2007 and placed in a jail cell without receiving medical attention.
The Humboldt County coroner listed his cause of death as a subdural hematoma due to blunt force trauma.
In reaching its verdict, the jury determined the officers used excessive force and were deliberately indifferent to Cotton's medical condition when they jailed him.
The beating came after Cotton's arrest for his alleged involvement in fights at a rescue mission.
A federal jury in Oakland found the city of Eureka and Officers Adam Laird and Justin Winkle liable for Cotton's death.
The Associated Press contributed to this report.