When 21-year-old Elka reported an alleged rape to Queensland police last year, she did not expect such an emotionally wrenching investigation.

She had met her alleged attacker on the popular dating application Tinder and, after weeks exchanging text messages and phone calls, went to his home to watch a film.

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"When I met him, I thought it was he was just like he was on the phone," Elka said.

"He was a very gentle kind of timid guy, but we had a very good rapport."

The next morning, she woke up with the man on top of her, naked.

"He had pinned my arms up beside my head," Elka said. "I can just remember feeling so, so confused and so vulnerable and not believing that this was happening."

The investigation

She fled the house covered in cuts and bruises, tears streaming down her face, and, after collapsing in the street, somehow gathered the courage to walk to the nearest police station.

"I was crying so hard," Elka said. "I was frantic. I was scared and confused about, you know, why is this happening to me."

Documents obtained by Lateline under a Freedom of Information request confirm that she presented to police immediately after the alleged attack on June 8, 2016.

Two police officers took her statement. A doctor inspected her injuries.

But then police asked Elka if she would confront her alleged attacker in a phone conversation.

What is a 'pretext' phone call? It is a phone call between the victim and suspect, who is unaware the conversation is being recorded

It is a phone call between the victim and suspect, who is unaware the conversation is being recorded The calls are usually initiated by the victim under the supervision of law enforcement officers

The calls are usually initiated by the victim under the supervision of law enforcement officers The purpose is to solicit incriminating statements linking the suspect to the crime

Police documents show that she was initially "refusing to to participate". Elka said she eventually relented to the police suggestion, believing her case would fail unless she agreed to participate.

"They basically said this is the best shot at having tangible evidence if it is to go to court," she said.

"'If you can get him to confess then that's all that we need. Otherwise it's really a case of your word against his.'"

The technique, known as a "pretext" phone call, is increasingly employed by police investigating sexual assault cases.

Evidence obtained as a result can implicate criminals in court. However, advocate groups say the calls can be traumatic for sexual assault survivors and deter them from reporting future attacks.

"It just felt really invasive," Elka said. "The fact that I had to have this very, very personal conversation about what happened to the person who did it."

She was coached about the kinds of questions to ask, had a recording device fitted to her clothes and was left alone to make the call as two police officers watched from outside the interview room.

"I just explained to him … that I just felt completely like he had done something wrong," she said.

"He agreed that he was very pushy and very aggressive. All sorts of things about his behaviour without actually saying outright 'I raped you'."

Queensland police concluded in their report that Elka's alleged attacker made a "partial admission" during the recorded conversation.

Despite this, and the physical evidence of her injuries, a few days later, Elka received unwelcome news. Police had dropped the case, citing a lack of evidence.

"We're told 'report it or it's not valid,'" she said. "And then when we do, we go through these really traumatising experiences."

One month later, Elka said she was sexually assaulted again in a separate incident. This time, she chose not to contact police. She did not want to be put in a situation where she might have to confront her attacker again.

Survivors 'not investigators', advocate says

For a person to be convicted of sexual assault, it needs to be established in court that the defendant had sex with the complainant without their consent, and that the defendant knew the complainant did not consent to the sex.

Kellie Wilk, a manager at the Gold Coast Centre Against Sexual Violence, said that survivors should not be put in a position where they feel emotionally responsible for investigating their own case.

"They're not the investigators," she said. "It's up to the police to look at any kind of evidence that they can find and look at a whole range of tools that help them collect that evidence."

Confessions obtained in pretext calls sometimes are not admitted as evidence in court, because police have not obtained warrants before the calls.

NSW Law Society president Pauline Wright says calls can interfere with legal rights. ( ABC News )

This means that a highly conclusive admission must be made by the accused, in order for it to be used as evidence.

Pauline Wright, president of the Law Society of NSW, said the calls can also interfere with accused perpetrators' rights to silence.

"If you know that you're being accused of a crime, then you've got the right to either make a statement or not make a statement," she said.

"The right to silence is there to protect people from saying things that can be misinterpreted later without the benefit of legal advice. People can be in stress when they're being questioned by police so that right to silence is quite important."

Victims considered when using pretext calls: police

In a statement, the Queensland Police Service told Lateline said pretext calls were one of many tools used to investigative crimes.

"There are a number of procedures surrounding use of the pretext conversations, including an assessment of the impact of the conversation on the victim and the benefits to the investigation."

But Elka said she felt the police did not consider the impact that the call would have on her.

"I definitely felt it was sold kind of as the hanging point on whether or not my rapist would ever face justice," she said.

"It's not fair that we need to be the ones to talk to them and get them to confess. I don't think that's our job as victims."