A man charged over the alleged gang rape of a 15-year-old girl at a party in his Blue Mountains home, west of Sydney, has been threatening her since his arrest, a court has heard.

Christian Dickens is one of three men charged with the aggravated sexual assault of the teenage girl in Hazelbrook in 2012.

Dickens and Aaron Jensen, 22, as well as a third man, who was 17 at time and cannot be named for legal reasons, were charged with aggravated sexual assault in company, detaining a person in company and resisting arrest.

A bail hearing in the Supreme Court heard that on the day the 21-year-old was arrested on December 23 last year he was recorded inside the cell area at Katoomba Police Station saying that if he got out the first thing he would do would be to "track down" the alleged victim.

"I just want you boys to know don't worry, that if I get out I'm going to take care of her one way or the other," Dickens was recorded as saying.

"There's going to be some very sorry people if we don't get locked up and of course, even more f*****g sorry if we do."

He was also alleged to have said: "the moment that judge goes 'not guilty', I'm just going to jump up and strangle the slut and get done for murder".

"F**k it, I'm going to jail, I've been preparing myself for this for a couple of weeks."

'He was trying to guilt me into changing my statement'

The court also heard Dickens put pressure on a key crown witness to change his statement to police.

The witness said: "he was trying to guilt me into changing my statement and asked me if there was any way for me to go back to police and either retract my statement of change what I had said."

A man brought into custody in the days after the alleged gang rape. ( Supplied: NSW Police )

The judge also said he had made certain admissions, and "expressed his regret" to the alleged victim after the party.

Dickens allegedly said: "I'm sorry for taking advantage of you when you were drunk, you could have said stop anytime, I shouldn't have done that."

The court heard that teenager had told police she pleaded with Dickens to stop on the night of the alleged sexual assault.

The judge also said Dickens had been recorded during a phone call with his mother while in custody making threatening comments about the officer investigating the case and saying he wanted a "copper in a noose".

Dickens' lawyer said he was prone to bluster and exaggeration and the threats were the frustration of a man in custody for the first time.

Threats 'impossible to dismiss', judge says

But Judge Geoffrey Bellew said the threats were "impossible to dismiss" as mere exaggeration and the court had concerns for the safety of the alleged victim and witnesses.

Police search the house in Hazelbrook where the alleged gang rape took place. ( Supplied: NSW Police )

The court heard it was Dickens who invited the 15-year-old to the party, after exchanging messages with her on Facebook the day before.

It is understood the party was held to celebrate Jensen's birthday, and was held at Dickens' house.

Allegations came to light after police formed a strike force to investigate historic sexual assaults, prompting the alleged victim to come forward.

During Dickens' original bail application, his lawyer, Danilo Rajkovic, argued his client was the "lesser aggressor" in the alleged incident.

He told the court his client had cooperated with police and had been remorseful.

However, the prosecution argued the girl's family was "gravely fearful" of him being given bail.

The court heard 20 witnesses would be appearing in court over the matter.

Dickens is due back in court on August 26, when he is expected to enter a plea.