Police have made a fresh appeal for a potential witness following the murder of Dr Gary Jenkins.
The mental health psychiatrist from Cardiff Bay died in hospital after he was allegedly attacked in the Bute Park area in July.
But following further enquiries, a clearer image of the unknown man has now been released.
Detective Chief Inspector Stuart Wales said: ''We believe he would have been in the vicinity of the top of Queen Street near its junction with St John Street at around 11.30pm on Monday July 19.''
''We understand he was then in the vicinity of the Esso garage at the bottom of Cathedral Road at 11.54pm before walking up Cathedral Road away from the city centre.''
''I must stress he has done nothing wrong but he may have important information that would further assist our enquiries in relation to what happened to Dr Gary Jenkins.''
Police are not looking for anyone else for anyone else in connection with the murder at the moment.
Chief Insepector Wales, the senior investigating officer, added: ''I would like to thank the community for the excellent support they have provided to this investigation to date, which has helped enormously.''
If you have any information in connection with the murder, contact South Wales Police on 101, quoting reference no. 254215, or Crimestoppers anonymously on 0800 555 111.
Dr Jenkins, who worked for the Cardiff and Vale health board, died in hospital 16 days after the alleged assault.
Jason Edwards (25), from Riverside, Lee Strickland (36), of no fixed abode, and a 16 year-old girl who can't be named for legal reasons, are due to go on trial in January, accused of murder.
All three are due to appear at Newport Crown Court for a plea hearing on Friday 15th October.