Marcus Faulk was charged with killing his cell mate Jason Cannon 15 years ago in Pleasant Valley State Prison.
The case has taken years to get to trial.
Prosecutors say Fresno County Sheriff's Detective Joel Wahlenmaier was investigating the case when he died in the line of duty back in 2010.
Prosecutors then filed the case in 2019.
But as it wound through the court system, attorneys ran into more delays because of the pandemic.
Prosecutors now have 60 days to retry the case and a new trial date is expected to be set during a hearing later this month.