She was murdered by Dennis McGrory, her aunt's 28-year-old estranged partner, who was described at his trial as being "wild with rage" when he sexually assaulted, stabbed, and strangled Montgomery at her family home in Offord Road.

He faced trial again in 2022 under the rule of double jeopardy after swabs taken at the time of the murder were tested for his DNA and found to be a one-in-a-billion match.

[3] Some time between 1 and 2 June 1975, it is believed that after a period of drinking heavily, McGrory, then aged 28, went to Montgomery's house in Offord Road, Islington, looking for Josie.

Her body was discovered on the floor of the lounge of the house when her father, Robert Montgomery, returned home in the early hours of 2 June.

The slip of paper bearing the aunt's address, which turned out to be false, placed him at the scene, and on 10 July 1975, he was charged with Montgomery's murder.

[2][1] The case was sent to the Court of Appeal, where the acquittal was quashed,[1] and on 3 March 2020, McGrory, by then living in Newport Pagnell, Milton Keynes, Buckinghamshire, was rearrested and once again charged with Montgomery's rape and murder.

[7] The trial was told that a burn mark on Montgomery's leg, along with the presence of the electric cord, suggested she may have been tortured by McGrory in order to reveal her aunt's location.

A page from the teenager's diary containing Josie's address was also torn from the book by McGrory, and found in his pocket at the time of his original arrest.

[5][9][11] Following the two week trial,[9] the jury was sent out on 19 December, and convicted McGrory of both the rape and murder of Jacqueline Montgomery, and a sentencing hearing was set for 13 January 2023.

[1][11] Speaking after the conviction, Montgomery's sister, Kathy, said: "The investigation of the last few years has meant revisiting memories of the murder which has caused pain and stress for me and my family and I am relieved that we finally have justice for Jackie.

"[7] Max Hill KC, the Director of Public Prosecutions for England and Wales, commented on the unusual nature of the conviction: "It is extremely rare for an acquittal to be overturned but after careful consideration I was satisfied there was new clear and compelling evidence to allow an application to be made to the Court of Appeal.

Presiding judge, Mr Justice Bryan, sentenced McGrory to life imprisonment with a minimum term of 25 years and 126 days.