Detectives investigating the death of Claudy man Conall Kerrigan revisited the scene on Sunday, September 27.
It is four weeks since Conall (25) died after, it is believed, falling from the City Walls in Londonderry.
Police say they do not believe his death was a result of a crime, but do want to speak to witnesses who may have seen Conall on the walls and can help establish what led up to his death.
Detective Inspector Conor McStravick, who is leading the enquiry, said: “The purpose of the revisit was to see if we could make contact with anyone who may have been on the walls four weeks ago at about the time Conall was there.
“He had been in a local public house and we believe he was on the walls and in Foyle Street for some time afterwards. A check of CCTV footage has produced an image of Conall on the walls at 3am.
The police have issued a photograph of someone they believe may have seen or spoken to Conall and wish to speak to him as a potential witness.
“This witness is believed to have left the area in a white taxi car which collected him and people with him in Foyle Street close to Sandino’s bar,” said DI McStravick.
“We are keen to establish as far is possible all of the circumstances on behalf of both the family and the Coroner.”