File on 4 tells the story behind the brutal killing of 16-year-old transgender schoolgirl Brianna Ghey. She was attacked in a park near Warrington in Cheshire on a Saturday afternoon in February 2023. Two teenagers, who were obsessed with murder and torture, have been convicted of her murder. In the build-up to the killing, they'd exchanged text messages outlining a details of their plan. Reporter Katie Barnfield speaks to Brianna’s mother and the detective involved in bringing her killers to justice.

Reporter: Katie BarnfieldProducer: Hayley MortimerTechnical Producer: Richard HannafordJournalism Assistant: Tim FernleyEditor: Carl Johnston