Convicted murderer Danny Deacon treated unfairly by the police, Northern Territory Court of Criminal Appeal told

CONFESSIONS obtained by undercover police investigating Danny Deacon should not have been seen by a jury because they undermined his credibility as a witness, the Court of Criminal Appeal has heard.

Danny Deacon is serving a life sentence for the murder of his wife, Carlie Sinclair. PICTURE: Nine News Darwin/NT Supreme Court

CONFESSIONS obtained by undercover police investigating Danny Deacon should not have been seen by a jury because they undermined his credibility as a witness, the Court of Criminal Appeal has heard.

In a part-heard application for leave to appeal on Wednesday, Deacon’s Barrister Jon Tippett QC said the Deacon’s confessions to undercover cops made his evidence to the jury look bad.

Deacon, now 46, is serving a life sentence for the murder of his wife, Carlie Sinclair, whose body he buried in a bush grave at Berry Springs.

A months-long sting was part of a police operation — code named Operation Samburu — and ended with Deacon leading police to Ms Sinclair’s gravesite in Berry Springs.

The operation remains the subject of extensive suppression orders preventing the full story of Deacon’s capture from being told.

The Crown has appealed Deacon’s 21 year and six month non-parole period, claiming it to be “manifestly inadequate”, while Deacon’s legal team argue much of the evidence gathered by the undercover team should not have been shown to the jury.

The court has reserved its decision on the Crown’s sentencing appeal.

The defence appeal is out-of-time, forcing Mr Tippett to convince Chief Justice Michael Grant, Justice Stephen Southwood and Justice Trevor Riley that he has a reasonable case to argue.

Barrister Jon Tippett QC leaves Darwin Supreme Court after Danny Deacon was found guilty of murder

The court heard Deacon’s proposed appeal, if successful, would have widespread implications for other undercover police operations around the country.

Chief Justice Michael Grant said it was a “high stakes” matter and Justice Stephen Southwood said if Deacon’s appeal was successful it “would end (that type of) operation, wouldn’t it?”

“It would and it should,” Mr Tippet said.

Mr Tippett said the type of undercover operation — which has been used to target high-profile cold case suspects — revolved around “institutionalised deceit” on the part of police.

The appeal revolves around whether Deacon’s confessions to undercover police were obtained as a result of “oppressive” police conduct.

“If the conduct is oppressive and it can be said ... that the conduct infected the admissions (of guilt) then it is out,” Mr Tippett said.

A successful appeal would likely result in a retrial with key evidence kept from the jury.

Deacon’s leave application was adjourned for further submissions on April 10.