The Police Ombudsman's Office has appealed for any witnesses to an arrest that took place in the William Street area of Derry/Londonderry on 19 February this year.
A spokesman for the Office said, "We are aware that there were people in the area who saw the incident, and that some people may even have filmed it on their mobile phones or other devices. We would be especially keen to hear from these people."
Anyone who feels they may be able to help is asked to phone the Police Ombudsman's Witness Appeal Line on 0800 032 7880.