A retired teacher and a state prison inmate arrested this week in the 1970 killing of a Berkeley police officer will not be charged, authorities said.

Though police said this week that they had new evidence, prosecutors said they don't have enough to charge former teacher Styles Price (search), 56, as the triggerman. Police said they decided not to pursue charges against Don Juan Graphenreed (search), currently imprisoned on drug charges, the alleged getaway driver.

Ronald Tsukamoto (search), 28, had been on the Berkeley police force less than a year when he was gunned down on Aug. 20, 1970. Authorities have said the shooting was carried out by Black Panthers (search) hoping to raise their stature in the militant group.

Price and Graphenreed were arrested Wednesday after police said they had discovered additional evidence using new technology.

But Berkeley police spokesman Joe Okies said the Alameda County (search) district attorney's office rejected the case against Price. Police still believe they arrested the right suspects, he said.

"Our investigators worked long and hard on this case," Okies said Friday. "They checked and rechecked the facts. We have identified the people responsible in this case."

Morris Jacobson, spokesman for the Alameda County district attorney's office, confirmed the men wouldn't be charged, but would not elaborate. When prosecutors decided they couldn't successfully prosecute Price, police decided not to pursue the charges against Graphenreed, Okies said.

Price's lawyer, William Du Bois, said a prosecutor called him Thursday to tell him charges would not be brought.

"This is consistent with my client's position from the beginning that he is categorically not responsible or in any way connected to this crime," Du Bois said.

In a jailhouse interview with the San Francisco Chronicle, the former high school social studies teacher said he was politically active in 1970 but denied any involvement in the killing. He said he had been framed by Graphenreed, a longtime friend.

"I was militant but I was nonviolent," said Price. "I swear on the souls of my mother and father."

Graphenreed, 56, was also arrested in the case last year, but Alameda County District Attorney Tom Orloff did not file charges at that time because prosecutors didn't have enough evidence.

David Hilliard, who was the Black Panthers' chief of staff, said the suspects weren't members of the movement and his group had nothing to do with the killing.

Tsukamoto was shot in the head at close range while he was chatting with a motorcyclist he had pulled over.