Convicted killer Luke Mitchell has launched a new appeal following the Supreme Court's Cadder ruling on suspects' rights to representation.
Mitchell, 22, was sentenced to life in 2005 after he was found guilty of murdering his girlfriend Jodi Jones, 14, in Dalkeith, Midlothian, in 2003.
He told the Appeal Court in Edinburgh his trial was unfair because he had no access to a lawyer during an interview.
The Cadder ruling has led to a review of some aspects of Scots criminal law.
The Supreme Court ruled in October that the Scottish system which allowed suspects to be held and questioned for six hours without access to a lawyer breached the European Convention on Human Rights (ECHR).
In light of that ruling, 867 cases were abandoned, including 60 serious cases, nine of which were High Court cases.
Mitchell, who was ordered to serve at least 20 years for murder, claims evidence taken from a police interview when he did not have access to a lawyer was "crucial" to the Crown case.
He went to the Appeal Court in Edinburgh asking for permission to have the claims, contained in a single ground of appeal, heard by the court.
In paperwork lodged with the court, lawyers for Mitchell state: "The decision in Cadder clearly applies to this case."
They note that Mitchell's initial appeal against conviction, which was thrown out in 2008, pre-dates the Supreme Court decision.
The ground of appeal centres around the use at his trial of his police interview when he was a suspect.
At the time of the interview he was 14 years old and did not have access to legal representation before or during the interview, it is claimed.
Mitchell's lawyers state in the official paperwork: "The evidence of the appellant's interview was relied upon by the Crown as crucial to the corroboration of the circumstantial Crown case.
"The use of this evidence rendered the appellant's trial unfair in the circumstances of this case."
Mitchell's legal team also note that Appeal Court judges have previously criticised as "outrageous" the way police interviewed him.
At the Appeal Court hearing, Maggie Scott QC argued that the new ground of appeal should be heard by the court, while the Crown opposed the move, saying it had come too late.
Scotland's top judge, Lord Justice General Lord Hamilton, sitting with Lords Osborne and Kingarth, will give their decision at a later date.
Jodi's mother Judith and several other family members were in court for the hearing. Mitchell's mother Corinne was also in court.
Earlier this month, an attempt by Mitchell to have his minimum jail term cut was thrown out.