The policeman had been initially charged with murder alongside two civilians who were present at the scene.
The two civilians were set freed after the court ruled hat they did not take part in the fatal assault of Githinji.
A police officer has been sentenced to 30 years in prison for killing an unarmed man in Nyandarua County six years ago.
While handing William Muriuki Nyaga the sentence, the High Court said the former police officer grossly abused his authority when he assaulted Stephen Githinji Ndiuni at Equator Springs Hotel in Gwa Kungu area, leaving him for dead.
