The sister of a slain human rights activist on Wednesday appealed a court ruling that freed an army colonel who had been convicted in the case. Col. Juan Valencia was convicted last year of ordering the killing of Myrna Mack, who was stabbed to death outside her Guatemala City office in 1990. Two other defendants were acquitted. An appeals court ruled earlier this month that there wasn’t sufficient evidence against Valencia and ordered him freed. On Wednesday, Mack’s sister Helen asked the Supreme Court of Justice to overturn the ruling and again try Valencia and the other two defendants, Gen. Edgar Godoy and Col. Juan Oliva, on murder charges. Full Story