CHINO, Calif. (KABC) -- After spending nearly 40 years in prison, a convicted killer has again been denied parole for the murder of a Cypress police officer.Bobby Joe Denney, now 72, will remain in state prison, but will be eligible for another parole hearing in five years, according to family members of the victim who attended Thursday's parole hearing.The hearing was held at the state prison in Chino.Denney was convicted in 1977 of killing Cypress police Sgt. Donald Sowma.The officer was responding to a burglary call at a medical clinic on Nov. 19, 1976. As he went inside, he was shot and killed by Denney.Sowma remains the only police officer for Cypress killed in the line of duty.At the time of the trial, there was no death penalty or even life without possibility of parole in California. So family members of Sowma and police officers have had to continue showing up at parole hearings over the years to keep Denney behind bars.Earlier Thursday, about two dozen protesters, many of them police officers, were outside the Chino state prison to express opposition to Denney's release."Seems like it opens a wound every time we go through this again," said Jim Sowma, the officer's son. "It's real hard, real hard. And as it gets closer we start losing sleep.""I don't think he should be able to get out and enjoy his family, because he took that away from them," said Mike Idom, a retired Cypress police captain who was a cadet in 1976 and worked with Sowma.