A Supreme Court ruling that a law has been wrongly interpreted for more than 30 years could help a triple killer’s appeal against his conviction.

Kevan Thakrar, of Lomond Way in Stevenage, is currently serving a minimum 35 year jail term after he and his brother, Miran, were convicted in 2008 of killing three men over a drug deal, and attempting to kill two women.

Kevan Thakrar has always maintained he was wrongly convicted and is now poised to launch an appeal.

But Kevan has always maintained he was wrongly convicted and is poised to launch an appeal.

He was found guilty under joint enterprise – a law which has been used against people in gang-related cases if defendants could have foreseen violent acts by their associates.

The Supreme Court ruled on Thursday that this law had been wrongly interpreted and it was an error to treat foresight of a crime as automatic authorisation of it.

A panel of five Supreme Court judges unanimously found “common law took a wrong turning” as far back as 1984 and “the law must be set back on the correct footing”.

The judgement went on to say: “This necessary correction does not mean every person convicted in the past as a secondary party, where this law was applied, will have suffered an unsafe conviction. The outcome may in many cases have been the same.”

Thakrar’s mum said after the announcement: “Kev already has an appeal ready to go to the Criminal Cases Review Commission – he’s waiting for the legal aid funding to come through. This ruling will help his case.”

On the same day as the Supreme Court ruling, Thakrar’s supporters held a protest at HM Prison Service headquarters in London asking for a new and fair trial, as well as his immediate release from solitary confinement.

Thakrar’s mum says he has been held in a close supervision centre – which holds about 60 men considered to be the most dangerous in the prison system – for six years and is suffering from post-traumatic stress disorder.

Keith Cowell, 52, his son Matthew, 17, and Tony Dulieu, 33, were lined up and shot with a sub-machine gun in Bishop’s Stortford in 2007.

Matthew Cowell’s girlfriend Clare Evans and a second woman, Christine Jennings, were stabbed after the killers ran out of ammunition. Both women, who were targeted because they were witnesses, survived.