An inquiry into an alleged assault by an officer in Manchester, which was captured on CCTV, is to be supervised by the Police Complaints Authority.
The CCTV footage was shown in court
A Greater Manchester Police officer has already been removed from front-line duties over his alleged involvement.
Video footage played in court apparently showed an officer repeatedly kicking Delbo King while on the ground.
The 33-year-old former paratrooper from Gorton, Greater Manchester says he wants the officer brought to justice.
The Police Complaints Authority (PCA) says the investigation into the allegations will be carried out by an outside force.
It will be supervised by PCA member, Duncan Gear, and a report will be submitted to the Crown Prosecution Service (CPS).
The CPS will then decide what, if any, charges will be brought.
Wendy Towers of the PCA told the BBC: "The video obviously raises a number of issues that have to be investigated.
"We have now asked for an external force to come in. We will supervise the [inquiry] so it will have a degree of independence from the police force."
The investigation was ordered after the CCTV footage was shown during a court hearing at which King admitted criminal damage.
He also pleaded guilty to disorderly behaviour and resisting a police officer in the execution of his duty.
King was given one day's detention and ordered to pay £100 compensation for damaging a bus shelter.
But his solicitor told the court that what had followed the offence by King was gratuitous violence on the part of the officer.
King said he was kicked several times in the head and face and twice in his testicles.
The video also appears to show him being sprayed with gas and bumping his head on the police van's rear door as he is taken into custody.
'Served Queen and country'
The former paratrooper told the Manchester Evening News: "I am sickened about the whole affair and I intend to seek justice.
"I am not some scumbag drug dealer - I have served Queen and country.
"I admit I was drunk, but I wasn't violent towards the police and after they cuffed me that should have been the end of the matter."
King admitted criminal damage and disorderly behaviour
A PCA spokeswoman said that following the outcome of the investigation, the PCA would liaise with Greater Manchester Police over any possible misconduct proceedings.
King's solicitor, Angela Taylor, said: "Because there are potential civil proceedings pending, it would be inappropriate to comment at this stage.
"People are going to see the video and make their own
conclusions from it."
And Councillor Stephen Murphy, from Greater Manchester Police Authority, said: "I think anybody who sees that graphic display will be extremely concerned.
"You normally see that coming from somewhere else and not from the British police service."