The Garda Ombudsman is investigating the circumstances surrounding the arrest of a teenager in Dublin last week.
A 17-year-old boy was arrested on suspicion of committing a public order offence in the city at around 9pm on Tuesday 1 June.
He was taken to Pearse Street Garda Station but subsequently transferred to hospital for treatment for head injuries.
A Garda superintendent referred the matter to the Garda Síochána Ombudsman Commission.
GSOC has appealed for witnesses and said it would like to hear from people that may have captured the incident on CCTV, dashcams or mobile footage.
Anyone with information which may be of assistance to the investigation is asked to contact GSOC at 1890 600 800 or email@example.com.