Jurors in the trial of lawyer Stephen Bingham toured San Quentin prison to see where six people died in a bloody 1971 escape attempt. Bingham, 44, is accused of giving a pistol to inmate-author George Jackson, who, authorities say, started the violence. Marin County Dist. Atty. Terry Boren said the jurors were shown the front gate of the prison and a metal detector where visitors are checked for contraband. Boren contends that a 9-millimeter automatic pistol was brought into the prison inside a tape recorder carried by Vanita Anderson, a legal investigator working with Jackson. He said that Bingham took the tape recorder into an interview room where he met with Jackson and that Jackson had the gun when he was returned to his cell. But former San Quentin guard Bernard C. Betts testified that he thoroughly checked the tape recorder, including its battery compartment, before allowing it inside the prison walls.