Jan Botha says the courts and social workers were to blame for the death of his son Jandre.
Four years ago, Botha laid criminal charges against his former wife and her lesbian partner for abusing his child.
A Mokopane (Potgietersrus) court dismissed the case against Hanelie Botha and Engeline de Nysschen. He later tried to gain custody of the child, but was denied.
Botha recounted how the court had failed to accept his version that the two women were mistreating his child soon after his divorce in 1999.
Commenting on their murder conviction on Wednesday, Botha said: "I am very happy that the court of Vereeniging has accepted my version of my child's abuse at the hands of the two, because the law and the social workers in Potgietersrus failed me.
"It was proven in court (Wednesday) that the social workers who recommended that Hanelie must get custody of Jandre did not do their job properly. I laid an assault charge against them four years ago."
A year before Jandre's death, the court dismissed the matter on the grounds that there was no evidence. This was even though Jandre had been absent from pre-school several times - proven now to be due to serial beatings.
"There was enough incriminating evidence against them, but they were let free. I'm happy that the prosecution in this case did its job properly," Botha said.