The Police Ombudsman's Office has appealed for information about an incident in Armagh city in the early hours of Sunday 15 May.
A spokesman said: "Police were dealing with disturbances in the Railway Street area at around 3am, but there is one incident in particular we are interested in. It involved a police officer and a young person in his late teens and happened as the youth crossed Railway Street between Micky Kelly's pub and the Premier One taxi offices."
Anyone who saw what happened is asked to contact the Police Ombudsman's freephone witness appeal line on 0800 032 7880.