A senior garda in the Marioara Rostas murder investigation has denied that the State's main witness received preferential treatment or demanded immunity in return for a statement against the accused.

Detective Superintendent JJ Keane was being cross examined at the Central Criminal Court in the trial of the Dublin man charged with murdering the teenager in the city.

Alan Wilson, 35, of New Street Gardens has pleaded not guilty to the 18-year-old's murder at O'Hanlon's house on Brabazon Street, The Coombe between 7 January and 8 January 2008.

The Romanian teenager disappeared on the afternoon of 6 January, after her brother saw her getting into a car with a man in the city centre. Her body was found in a shallow grave on the Wicklow border four years later. She had died of four bullet wounds to her head.

The accused man's former friend, Fergus O'Hanlon, has testified that he arrived home on 8 January 2008 to find Ms Rostas with a hole in her forehead and Mr Wilson holding a gun.

The 37-year-old convicted criminal, who has been granted immunity from prosecution, said he helped the accused bury her body in the Dublin Mountains.

Det Supt Keane testified of Mr O'Hanlon's involvement in the investigation, including his request to meet senior gardaí in late 2011 to say he had information about the case.

Under cross examination by Michael O'Higgins Senior Counsel, defending, he said Mr O'Hanlon had not received any preferential treatment at that time.

However, he agreed that he had received a suspended sentence for district court offences some weeks later, after a superintendent told the judge that he was assisting in a murder investigation.

He was asked if Mr O'Hanlon had requested immunity from prosecution before giving his statement.

"At no stage was immunity ever mentioned," he replied.

Sergeant Seán McAvinchey said that Mr O'Hanlon never looked for immunity from him either.

He said that when Mr O'Hanlon asked him: 'Will you do a deal in front of a solicitor?' he took it to mean that he wanted his solicitor present.

He said he believed that Mr O'Hanlon didn't care about the consequences for himself.

He agreed that Mr O'Hanlon's girlfriend had told him that he feared being arrested when he identified the burial site. The sergeant agreed that he assured him that this was not the case.

Mr O'Higgins then read a memo taken by Mr O'Hanlon's solicitor of a meeting with Sgt McAvinchey and a colleague before her client gave his statement. She had written that they told her that Mr O'Hanlon had asked for immunity.

"Absolute nonsense," said Sgt McAvinchey.

"We were offering no deals," he added later. "We were offering nothing in return for information."

Inspector Michael Cryan was also cross examined by Mr O'Higgins. He asked him if alarm bells had gone off when it was realised that Mr O'Hanlon had previously faked a shooting and had described another shooting as having happened in two different locations.

Insp Cryan agreed that it didn't seem to have been put to Mr O'Hanlon.

"This ought to have been followed up on," suggested Mr O'Higgins. "If you have a situation where a witness is, at will, making up stories about people shooting him, it goes to the heart of his credibility."

"If he's making it up, yes," responded the inspector.

The trial continues before Mr Justice Patrick McCarthy and a jury of 10 men and two women.