Luke Mitchell's arrogance when questioned about the murder of his girlfriend Jodi Jones led to his downfall, appeal judges heard yesterday.

Defence QC Donald Findlay has tried to convince the Court of Criminal Appeal in Edinburgh that Mitchell, then a 15-year-old schoolboy, was "grilled" and interrogated by bullying detectives who were trying to force a confession from him, weeks after Jodi's body was found in woods near her home in Dalkeith, Midlothian.

Appeal judges were yesterday told the hoped-for confession never came but that Mitchell showed he was a liar.

The jury at Mitchell's trial heard eight controversial extracts from the police interview. Judge Lord Nimmo Smith rejected a defence attempt to block the evidence, saying that Mitchell seemed able to stand up for himself.

Judges hearing an eighth day of legal argument in Mitchell's attempt to overturn his murder conviction were asked to back Lord Nimmo Smith's ruling.

They were shown how the schoolboy had answered back, insulting the officers and calling one "a f***ing retard".

Advocate-depute John Beckett, QC, for the Crown, insisted there was good reason to let the jury hear parts of the interview - to expose Mitchell as a liar.

Allan Turnbull, QC, who prosecuted Mitchell, wanted to use answers Mitchell gave detectives to destroy his alibi, among other things.

Appeal judges were told that in his speech to the jury three years ago, Mr Turnbull described the interview with police by saying: "Mitchell lied consistently and arrogantly to them. You cannot believe a word that comes out of his mouth unless you can independently verify it."

Yesterday, Mr Beckett told the appeal court that some of the questioning by detectives was "unsatisfactory" but denied there were any tricks - such as an attempt to play "good cop, bad cop" and repeating questions without giving Mitchell the chance to reply.

Lord Nimmo Smith, in a note to appeal judges about why he allowed the jury to hear the interview, said: "Mitchell was entirely able to stand up for himself. Indeed, he mocked, ridiculed and insulted the officers interviewing him."

Mitchell, said the trial judge, "gave as good as he got and was not pressured into making any admissions".

Urging the appeal court to reject claims of a miscarriage of justice, Mr Beckett said it was instructive to see how Mitchell coped with the more forceful types of questioning. He said: "As my lords know, he was never broken. He never made any confession."

The advocate-depute added: "I suspect there are many gentlemen of 30 or 50 or 60, interviewed by the police, who don't have whatever the characteristic may be to speak back to the police in this manner."

The hearing continues next Thursday.