Sofia City Court acquitted Friday Yordan Kolev, who was charged with a bomb attack and the murders of a pharmacist woman in October 2002.
The prosecution pointed Kolev and Mincho Pavlov as the killer, who planted the bomb in the car and Mario Ivanov from the town of Pleven as the man who ordered the murder.
Ivanov, dubbed the boxer was shot to death a year later on April 4, 2003.
Pharmacist Hristomira Atanassova, 39, was driving the car when the bomb exploded at29 Tsar Ivan Shishman Street in the capital morning. The blast took place at the entrance of 7th Sofia high-school "Sveti Sedmochislenitsi" in downtown Sofia.
The car exploded in motion at 8am in front of the entrance of the school. Atanassova was taken to the hospital where she died. Witnesses said that the woman was crying for help immediately after the blast and her legs were lacerated
The explosive device had been planted on the outside of the driver's section of the car, the Interior Ministry press office said.
Police presumed that the car blast place for personal reasons.