The phrase "actual perpetrators" refers to the people who were really responsible for a certain action or crime. These individuals are the ones who directly carried out the wrongdoing. Full definition
An eye for an eye might apply if the actual perpetrators were killed. (religion.blogs.cnn.com)
All speculations about who the bombers could be, Caucasian, Muslim jihadist, American citizen, foreign born, all seem to be true; all of these possibilities assimilate in the actual perpetrators of the crime. (firstthings.com)
Separate research by the Innocence Project into 23 DNA exonerations in New York found that police had identified the actual perpetrators in 10 cases, nine of whom had gone on to commit new crimes while wrongfully convicted defendants sat in prison. (legalblogwatch.typepad.com)