A Bronx family is moving to file a lawsuit after they say police left their teenage daughter alone in a cell with a sweater even after she told them she was suicidal, and did not intervene when she hanged herself.

The family filed legal papers Friday asking for a court order to compel the NYPD to preserve and turn over all records related to the case.

In a petition filed in Manhattan Supreme Court, attorneys for Saniyah Cheatham's family wrote that the NYPD’s failure to address the 18-year-old’s mental health conditions or monitor her while in custody “directly resulted in her untimely death.”

City medical examiners in July officially ruled Cheatham’s death a suicide.

Attorneys said Cheatham was experiencing acute mental distress when she was arrested on assault charges. After police took her to the 41st Precinct in Longwood, Cheatham “stated that she would attempt suicide if left in a cell.”

Despite this, the family alleges officers left Cheatham alone in a holding cell with a sweater, which she used to hang herself.

“Ms. Cheatham was visible within the holding cell and on surveillance video as she hanged herself,” according to the court filing. “However, NYPD officers failed to intervene or provide her with any medical assistance.”

The petition also claims that Cheatham was being “unlawfully detained” at the precinct.

Representatives for the NYPD and the city's law department did not immediately return requests for comment.

The family initially questioned the medical examiner’s ruling that their daughter died by suicide, citing a lack of information shared with them and the fact they didn’t recall Cheatham wearing a sweater when they last saw her at a July 4 barbecue.

The Cheatham family is being represented by the law firm of Ben Crump, a nationally known civil rights attorney who has represented relatives of people killed by police, including Michael Brown, Breonna Taylor and George Floyd.

If you or someone you know is experiencing a mental health crisis, call 988 or visit NYC 988 online.