Double jeopardy meaning: UK law as Dennis McGrory jailed for Jacqui Montgomery murder - sentence explained

In the oldest double jeopardy case in England and Wales, a killer rapist who murdered a teenager nearly 50 years ago has been sentenced to life in prison with a minimum term of 25 years and 126 days.

When Jacqui Montgomery, then 15, was sexually abused, stabbed and strangled in her Islington, north London, home in 1975, Dennis McGrory was 28 years old.

The following year, the now 75-year-old was exonerated of the crime on judge’s orders, but decades later, he has been found guilty after DNA samples taken from Montgomery’s body revealed a one-in-a-billion match.

After a 2003 change in the law on double jeopardy, McGrory’s case was referred to the Court of Appeal and sent for a fresh trial at the Old Bailey. Here is everything you need to know about it.

What did McGrory do?

Jurors were told McGrory had been “wild with rage” when he murdered Jacqui as he tried to track down his ex-partner Josie Montgomery, who was the victim’s aunt. During the attack, he ripped out a page of the teenager’s diary with her aunt’s address on it.

Jacqui’s body was found by her father, Robert Montgomery, lying on the floor of their living room in Offord Road in the early hours of June 2, 1975. She had suffered fatal stab wounds as well as blunt force trauma to the face and been strangled with the flex of an iron.

McGrory had threatened to rape Jacqui in the past and, on that night, he “made good” on those words, jurors were told.

How long has he been sentenced for?

The “abhorrent” killer has been told by a judge he will likely spend the rest of his life behind bars. On Friday (13 January) at Huntingdon Crown Court, Mr Justice Bryan jailed him for life with a minimum term of 25 years and 126 days, and described the killer’s crimes as “hideous” – saying the idea a man could inflict that level of violence on a 15-year-old girl “beggars belief”.

Sentencing McGrory, who appeared via video-link from HMP Peterborough on Friday, Mr Justice Bryan told the killer: “I have no doubt whatsoever that you intended to kill her in your brutal attack on her.

“You put Jacqui through a horrific, violent and sustained ordeal in her own home – a place where she was entitled to feel safe. In the decades that followed, you must have thought you had gotten away with your hideous crimes.

“How any man could inflict such sexual violence on a 15-year-old child that had done them no harm beggars belief. You have shown not one iota of remorse or compassion for Jacqui or Jacqui’s family. You cut short that life and deprived her of that life, and all the things she hoped for in that life.”

What is double jeopardy?

Double jeopardy is a legal defence that prevents an accused person from being tried again on the same (or similar) charges following an acquittal or conviction.

That meant that McGrory could not be put to retrial, as he had been acquitted by a judge previously. But a 2003 change in the law meant a retrial became possible.

That change was brought in following the murder of Stephen Lawrence and the Macpherson Report, which recommended that the double jeopardy rule should be void in murder cases, and that it should be possible to subject an acquitted murder suspect to a second trial if "fresh and viable" new evidence later came to light.