Glen Coleman met the 19-year-old at Windsor Police Station in February 2022 after she came in to make a complaint that her cousin had threatened to share naked images of her online.
Over the next few months, the sex crimes officer met the woman multiple times at two parks in western Sydney and at the police station where he is alleged to have sexually assaulted her.
After finding out the alleged victim, who cannot be legally named, had gone for an interview at a Sydney strip club, he allegedly begged her to pay for sex or erotic dances.
Coleman faced Penrith District Court on Monday when a trial in front of 12 jurors began.
Coleman pleaded not guilty to three counts of sexual assault and seven other charges. (Miklos Bolza/AAP PHOTOS)
He has pleaded not guilty to one count of abusing his position of public office to procure the woman for his own sexual gratification, three of sexual intercourse without consent and six of sexual touching without consent.
"The behaviour of the accused between March and May 2022 shows the accused had a sexual interest in (the complainant) and that he acted on that sexual interest," crown prosecutor Kate Nightingale said on Monday.
At the time the alleged victim was living in shared housing for teenagers at risk of homelessness, jurors heard.
During an interview in late March 2022, the woman noticed Coleman had an erection, Ms Nightingale said.
"I am so hard for you," he allegedly told her.
Meeting at a park, he asked if she could dance naked for him before grabbing her breasts and genitals, the jury heard.
"I expect she will tell you she did not feel she could leave because he was a police officer," Ms Nightingale said.
He allegedly began texting the teenager in April 2022, asking her to send intimate, naked images and requesting sex for money.
Calling her "bubs" and "gorgeous" by text and Snapchat message, he eventually met with her at Windsor police station where she was sexually assaulted in one of the interview rooms, the jury was told.
In a Snapchat message in May 2022, Coleman offered her $700 for two hours of sex.
"You will wear a dress and a lacy g-string," he allegedly wrote.
"Bring another unless you want to go without undies as I will be keeping it."
Coleman did not deny that he had sex with the woman at a police station but said it was consensual. (Paul Miller/AAP PHOTOS)
The alleged victim did not read this message, instead showing it to two of her friends, one of whose parents were both police officers.
An investigation into Coleman was launched on May 12 and he was arrested eight days later.
In a document found on his police computer, the detective wrote it was the complainant who proposed being paid money for sex.
While there was no mention of sexual contact, the document referred to the sending of intimate images.
Ms Nightingale said while Coleman had sent photos of his genitals, the woman had not reciprocated.
DNA swabs from her underwear and dress worn when she was allegedly sexually assaulted in Windsor police station showed links with the sex crimes detective, the court was told.
Defence barrister Joel Brook said his client vehemently rejected the allegations.
"Mr Coleman denies he ever sexually touched or had sexual intercourse with the complainant without her free and voluntary consent," he said.
The officer did not deny he had sex with the woman at Windsor police station but said these acts were consensual.
He also contested the alleged sexual touching that she claimed happened in his car at the two parks.
The complainant began giving evidence by video-link on Monday afternoon and will continue on Tuesday.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
11°C