The appeal judges confirmed the judgment and the sentence rendered in first instance, according to the organization.
In May, Byuma, also a well known fiction author in his country, had been sentenced to 19 years in prison by the gacaca (pronounced gatchatcha) court of the Biryogo sector, in Kigali.
He had been found guilty of "criminal conspiracy" and violence against a Tutsi woman during the 1994 genocide.
The trial had been criticized by certain Rwandan and international human rights associations, including Human Rights Watch (HRW).
Member of several Rwandan human rights organizations, Byuma is president of the "Turengere abana" (Let us protect the children) association which, in a report, had accused Judge Sudi Imanzi, president of the gacaca court of Biryogo, of having raped a young girl.
Byuma can still ask for the revision of his trial, a recourse available by the gacaca courts law.
The "gacacas", popular courts inspired by ancestral village assemblies where wisemen settled disagreements sitting on the grass (gacaca in the kinyarwanda language), can try all persons to have allegedly been involved in the genocide; except for organizers and rapists, who are tried by the conventional courts.
The 1994 genocide, perpetrated by Hutu extremists, resulted, according to the Rwandan government, in nearly a million killed, primarily within the Tutsi community.
© Hirondelle News Agency