The Police Department should have investigated 90% of the sexual assault reports it ignored in 1989 and 1990, an internal investigation has concluded. Since reopening the reports, police have gathered enough new evidence to arrest one man, present two cases to the district attorney and prosecute another man on an unrelated charge, the department said. "The fault was ours--it's that simple," Oakland Police Chief George Hart said. He will present the results to the City Council. Police administrators called for the investigation in January after the San Francisco Examiner revealed that nearly one in four women who reported a rape or an attempted rape were ignored.