South Africa’s National Prosecuting Authority (NPA) announced Tuesday that it has filed formal papers appealing the verdict and sentence handed to former Olympian Oscar Pistorius. The athlete received a five-year sentence for culpable homicide for killing his girlfriend Reeva Steenkamp on Feb. 14, 2013. Experts said that sentence could translate to less than two years behind bars. Presiding Judge Thokozile Masipa was criticized by some legal experts for ruling there wasn’t sufficient evidence presented during the seven-month trial to convict Pistorius of premeditated murder. “The appeal on conviction is based on the question of law,” said the NPA in a statement released Tuesday.