Robert Graham, 46, who denies attacking former deputy chief executive of the Law Society of Scotland Leslie Cumming, told court that he in-fact saved the 68-year-old from receiving a worse beating.
But today at the High Court in Edinburgh that version was ridiculed by the prosecution.
Mr Cumming was attacked with a knife outside his Murrayfield home in January 2006, leaving him permanently scarred.
And in her closing speech, solicitor general for Scotland Lesley Thomson QC, told jurors of Graham: “He told lies about what he did that night. He told lies with the aim of escaping a guilty verdict.
“It is an unusual case because while no-one saw Robert Graham’s face and is able to identify him from that night and no one heard his New Zealand accent, there is in my submission compelling evidence of a scientific nature to bring the crime home to Robert Graham.
“He left behind a part of himself. He left behind DNA.”
Defence counsel Mhairi Richards QC said there had been sloppy work in relation to the forensic analysis carried out.
She maintained that looking at the DNA evidence the jury could not be satisfied with it and said: “You can’t be satisfied with the quality of the evidence. You can’t be satisfied with the extent of the evidence.”
The trial continues.