A former chief of Chile's secret police was sentenced to 15 years in prison Thursday for the disappearance of a dissident during the dictatorship of the late General Augusto Pinochet. Retired General Manuel Contreras, who commanded Pinochet's feared secret police, was found guilty of the disappearance of Marcelo Salinas, who was never seen again after his 1974 arrest and is presumed dead. Chile in recent years has pushed to prosecute human-rights violations from the 1973-1990 dictatorship of Pinochet, who died in 2006. Thursday's was the 100th conviction resulting from abuses during the era, the court in Santiago said. Contreras already was imprisoned for convictions in other cases, including the 1976 bombing that killed prominent Pinochet opponent Orlando Letelier in Washington. Contreras already has accumulated prison terms totaling 57 years, and is involved in cases that could add another 197 years. Judge Alejandro Solis also sentenced four other officers to prison on Thursday, including Contreras' deputy commander in the secret police and former General Pedro Espinoza.