The Nigeria Police Force, NPF, has demoted the policemen who slapped a civilian on a road at Emouha in Rivers State.
The security agency acted following complaints and findings on video evidence widely circulated on social media on April 9.
The policeman and his colleagues were arrested last week for assault, discreditable conduct, and incivility to members of the public.
After an orderly room trial by the Force Provost Marshal, Adejoh Siaka has been reduced in rank from Inspector to Sergeant.
A statement by Force Public Relations Officer, CSP Muyiwa Adejobi said Sergeant Ndiwa Kpuebari, who was present at the scene but failed to discourage Siaka, was reprimanded.
Inspector Friday Obaka, discovered to have been absent from the scene of the skirmish, was discharged unconditionally at the conclusion of the proceedings.
The policemen will be posted out of Rivers State to other Commands and Formations to continue their police duties, Adejobi added.
The Inspector General of Police, Usman Baba, has tasked officers and men of the Force to be diligent, uphold the tenets of professional policing, and respect human rights