James Dwyer SC, for the now 17-year-old who was known as Boy B during his trial, said that the prosecution relied heavily on those interviews and without them there would have been "almost no evidence against him".
He said senior forensic psychologist Professor Susan Young had watched videos of the interviews and found they were "inadequate" and "inappropriate" for a 13-year-old boy given their duration, the use of manipulation and pressure, repetition and enactment.
The professor found that interviewing detectives engaged in an "overriding of caution" in the context of the defendant being a 13-year-old boy at the time.
Boy B's lawyers want to introduce Professor Young's report, which was reviewed by Professor Gisli Gudjonsson, as fresh evidence so that they can argue that the garda interviews should not have been presented in evidence at his trial.
Brendan Grehan SC for the Director of Public Prosecutions told the three-judge court that Boy B has never disputed the final account given by him to gardai in those interviews.
Instead, his lawyers used those interviews to suggest to the jury in his trial that he was just an innocent bystander who witnessed what his co-accused Boy A had done but did not participate in Ana's murder. Counsel said that in subsequent interviews Boy B has given to probation officers and psychologists he has given the same account with some added details.
Mr Grehan said he stands "one hundred per cent" behind the conduct of the detectives who interviewed Boy B. He told the court that the detectives had implored Boy B to tell them the truth in circumstances where they knew he was lying. They did so without raising their voices and used "perfectly valid" techniques for building rapport, counsel said.
President of the Court of Appeal Mr Justice George Birmingham, with Mr Justice John Edwards and Ms Justice Isobel Kennedy, reserved judgment on the application, saying the court intends to give its decision before the end of the legal term in late July.
Boy B and his co-accused Boy A were found guilty by a Central Criminal Court jury in June 2019 of murdering Ana at a derelict house in St Catherine’s Park in Lucan in May 2018. Boy A was also convicted of Ana's aggravated sexual assault in a manner that involved serious violence. Boy B lured Ana to the house on the pretext that Boy A wanted to meet her. When she arrived Boy A launched a violent attack on her.
Boy B was sentenced to 15 years’ detention, to be reviewed after eight years.
Boy A was sentenced to life imprisonment with a review after 12 years, and eight years imprisonment for aggravated sexual assault. No appeal has been lodged on Boy A's behalf.