A secretly made documentary expanding on allegations of sexual assault against supreme court justice Brett Kavanaugh has premiered at this year’s Sundance film festival.

Justice, a last-minute addition to the schedule, aims to shine a light not only on the women who have accused Kavanaugh, a Donald Trump nominee, but also the failed FBI investigation into the allegations.

Kavanaugh was also accused of sexual misconduct by Deborah Ramirez, who alleged that he exposed himself and thrust his penis at her face without her consent at a college party.

The first scene features Ford, half off-camera, interviewed by the film’s director Doug Liman, whose credits include Mr and Mrs Smith and The Bourne Identity.

Ramirez’s lawyers claim they contacted Republican senator Jeff Flake, who was involved in Kavanaugh’s confirmation hearings, to explain what happened to her.

He was frustrated by the FBI investigation into Kavanaugh that “never happened”, and sought the help of renowned documentary producers Liz Garbus and Herdy, both with specialised experience of films about sexual assault allegations, to do the work that he saw as unfinished, if barely started at all.