A box full of Polaroid photos of “nude and scantily clad women” was once found on the dashboard of a Chicago Police vehicle used by an officer who would later admit he paid young girls for sex before landing a 25-year prison sentence.

That’s according to a federal lawsuit filed Thursday against the city of Chicago and William Whitley, a former Chicago Police Department veteran now serving time in a Texas prison after pleading guilty last year to sex trafficking of a minor.

The lawsuit, filed by one of Whitley’s victims under the pseudonym “Jane Doe,” alleges the city let Whitley “act with impunity and to use his police power to lure and intimidate his victims without fear of repercussion.”

After he joined CPD in 1991, the lawsuit claims Whitley racked up at least 29 complaints. Seven were sustained, but only two of those came from civilians. The rest came from “higher ranking officials” within CPD. Half of the complaints that were not sustained involved verbal abuse or excessive force against civilians, and the majority of them were women.

Additionally, in one 2001 complaint, the lawsuit said Whitley was accused of leaving 46 “color Polaroids of nude and scantily clad women in a box on the [front] dashboard of his department vehicle.”

“These were apparently homemade Polaroid photographs, presumably taken by Officer Whitley, that should have raised alarm bells within the Chicago Police Department of Officer Whitley’s predatory nature toward women,” the lawsuit states.

The complaint was not sustained, it said, because the car had gone unused for a shift, and “investigators supposedly could not determine with certainty whether someone planted the Polaroids on the dashboard after Officer Whitley’s shift.”

A grand jury accused Whitley in 2017 of trafficking four teenage girls for sex as well as producing child pornography. That followed a 2015 FBI investigation that authorities said led them to Whitley.

When confronted, Whitley acknowledged he saw braces on the teeth of a 14-year-old girl he paid for sex — apparently the “Jane Doe” who filed the lawsuit Thursday — but he said he did not know her age. She apparently told him she was 23.

Before pleading guilty last year, Whitley insisted that braces “don’t dictate a person’s age.”

That same 14-year-old had been arrested in September 2015, but she told authorities about her “johns,” including Whitley, according to court records. She said she was introduced to him in June 2015 and had sex with him about five times, collecting between $60 and $150 from Whitley each time.

She said he also wore a gold chain with the CPD logo on it. And at times, she said, he bragged about being a cop.

The feds said Whitley was in touch with the girl by phone “hundreds of times” between July 24, 2015, and Sept. 17, 2015. Once, after he began texting the girl, she replied, “Awww ok wassup then.” And he replied, “You already know” and added, “B4 I gotta work.”

The girl also said Whitley took naked photographs of her inside his apartment.