The massacre at Camp Speicher, near Tikrit, was carried out by fighters from so-called Islamic State (IS) as it seized territory across northern Iraq.
Outrage over the massacre of the mostly Shia cadets helped mobilise Iraq's Shia militias in the fight against IS.
IS militants released photos and video documenting the massacre in 2014. Mass graves were found a year later.
The graves were discovered when Iraqi government forces recaptured the area.
