During the prosecution's opening statements today, the court heard how William Jones walked to Claude Road that night in April from his father's house nearby, looking for his girlfriend, who he believed to be with another man at a property in the area.
The prosecution said Mr Jones admits being in Claude Road, and knocking on the door of Peter Lewis' flat. They said he will claim that Mr Lewis threatened him with a knife, which he grabbed and hit him with, accidentally stabbing him.
William Jones denies murder, and the case continues.
More top news
A night of two halves - cold under clear skies in the south, with cloud and mist around the hills in the north!
The partner of a man critically injured in a crash in Cardiff has appealed for witnesses to come forward.
There are calls for the Welsh Government to change the law to force councils to collect rubbish at least once a fortnight.