Even bystanders can find themselves convicted of murder under a legal doctrine known as “joint enterprise”. The centuries-old principle enables gang members to be prosecuted for a murder even when there is no evidence as to who inflicted the fatal blow.

It was famously used in 1952 to convict Derek Bentley of the shooting of a police officer: his words, “let him have it”, were taken as evidence that he was a party to the killing. The murder was committed by his accomplice, Christopher Craig, but because Craig was then only 16, he escaped the death penalty. Bentley was hanged for the crime.

More recently, Tyrone Clarke, 16, was beaten and stabbed to death by a mob of up to 30 youths in Leeds in 2004. Four men were convicted, although none may have struck the fatal blow.

Joint enterprise allows police to prosecute someone if that person knew that an associate might kill or inflict serious harm, which means killers cannot hide their identity within a group.

There are concerns that people on the fringes of gang violence could find themselves facing life as a result of the doctrine when they just happened to be present at a murder.

In the trial of Samantha Joseph, however, the court was told that the death of Shakilus Townsend was pre-planned. There is no question that she was far from an innocent bystander.

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