Mr Ayiaorga is charged with abduction and defilement.
The defendants are being prosecuted on charges of criminal conspiracy, armed robbery, and illegal possession of firearms.
They were charged with criminal conspiracy, trespass, culpable homicide and illegal possession of firearms.
The herder, however, pleaded not guilty to charges of conspiracy, open grazing and damage to crops.
The prosecutor said that Mr Nengem and 16 others were arrested during police investigation for committing the crime while others are still at large.
The suspects had lodged in a guest inn where they were, following a tip off, arrested by the police with the fresh female head.
