A pensioner has been convicted under the double jeopardy law of raping and murdering his niece in 1975, after compelling DNA evidence against him was found.

Dennis McGrory, 75, of Milton Keynes, was found guilty by a jury at Huntingdon Crown Court on Monday, (December 19) of the rape and murder of 15-year-old Jacqueline Montgomery in Islington.

He will be sentenced at the same court on January 13.

The conviction reverses an earlier acquittal delivered by a judge 46 years ago.

A review of the case by Met detectives and forensic scientists in 2015 established that DNA found on the victim was one billion times more likely to belong to McGrory than anyone else, Scotland Yard said.

This new significant evidence was presented to the Court of Appeal, who agreed that the original decision should be quashed and a re-trial held.

This Is Local London: Jacqui Montgomery was raped and murdered by Dennis McGrory when only 15 years old in 1975Jacqui Montgomery was raped and murdered by Dennis McGrory when only 15 years old in 1975 (Image: Met)

Jacqueline's body was discovered by her father in the early hours of  June 2 1975 at their home address in Offord Road. 

A post-mortem revealed she had been stabbed several times, strangled with the flex of an iron, and received blunt force trauma injuries to her face, police said. 

The scene also showed signs that she had been sexually assaulted. 

The state of the room was consistent with a struggle and the phone was off the hook, supporting the fact the line was engaged from late on the morning of June 1, indicating the murder likely took place before this time. 

Jacqueline's family believe the disturbed phone was an attempt by her to call for help.

Jacqueline's sister, Kathy, said: “Jacqui and I always said that we could trust no-one. 

"A violent man who had been living within our family (raped and) murdered my sister. 

"He has been able to live his life. He has spent nearly fifty years as a free man doing as he pleased. 

"I find that unbearable when my sister didn’t even reach her sixteenth birthday. 

"His actions caused trauma to so many people and there were no consequences for him. 

"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 Jacqui.”

At the time of the murder, McGrory was the ex-long term partner of Jacqueline's aunt. He was swiftly arrested in connection with the incident and taken into custody.

Met officers said images taken of him at the time revealed visible injuries, including a bruised lip and long scratch to his neck, and smaller scratches to his wrist and arm.

He was charged with Jacqueline’s murder on July 10 but was later acquitted by a jury following a direction from the judge.

Following a request from Jackie's family, the case was reopened in 2015.

On 3 March 2020, McGrory was re-arrested for Jacqueline’s murder at his home address in Milton Keynes. 

He was charged with her murder for the second time in June 2020, 45 years after she was killed.

Det Con Jane Mascall, from the Met’s Specialist Casework Team, said: “In 1975 there was no way of testing for DNA, and detectives at the time relied on other forms of evidence. 

"Although McGrory was charged with Jacqueline’s murder, he was acquitted at trial which was a devastating outcome for her family.

This Is Local London: A swab that captured Dennis McGrory 46 years after raping and killing Jacqueline MontgomeryA swab that captured Dennis McGrory 46 years after raping and killing Jacqueline Montgomery (Image: Met)

"Many years later, a forensic review of the case meant we were able to take advantage of advancements in DNA technology, and we discovered a trace of McGrory’s DNA on a swab taken from Jacqui. 

"This new and compelling evidence meant that, working in close liaison with our colleagues from the Crown Prosecution Service, we were able to apply double jeopardy legislation to ensure he finally faced justice. 

"Jacqui’s sister, Kathy, was determined that this case should not be forgotten and I hope for her sake, and the rest of Jacqui’s family, that this outcome will provide some comfort.”

Det Supt Rebecca Reeves, Central Specialist Crime, said: 

“I hope this case, in its own way, sends a message to domestic violence offenders today about the determination of police and prosecutors to make London safer for women and children.”