Tanya Watts says thugs such as Shauna Hoare, who killed the 16-year-old with boyfriend Nathan Matthews, could use the ruling to appeal their sentences

The mum of tragic Becky Watts fears her daughter will be robbed of justice if the woman involved in her killing is freed under a new ruling.Tanya Watts spoke after the Supreme Court declared the joint enterprise law – where a suspect can be found guilty of murder by being part of the attack – has been wrongly used in courts since 1984.It could pave the way for the quashing of more than 600 convictions – including those ofStephen Lawrencekillers David Norris and Gary Dobson.Today’s ruling says those of the periphery of deadly attacks who had no “foresight” a death was going to happen should be considered guilty of murder.Experts insist the law would prevent miscarriages of justice.
But Tanya fears thugs such as Shauna Hoare, who killed her 16-year-old daughter with boyfriendNathan Matthews, 28, could use the ruling to appeal their sentences.As she prepared to mark the first­anniversary ofBecky’s horrific deathat the hands of her step-brother Matthews in Bristol, she said: “I thinkif they were to lessen Shauna’s sentence it would let Becky down, and other victims too, and make the justice system a joke.“If she gets a lesser sentence, otherswill think like that.“It will cause more trouble. We will get more copycats. Look how they treated my daughter. It will be a lesson for the justice system.“These people shouldn’t be walking the streets. She’s evil. They didn’t just murder her, it’s what they did after."No one should ever do that to another human being.”

Becky’s chopped up body was foundin a garden shed.Tanya is divorced from Becky’s dad Darren Galsworthy, who lives with second wife Anjie – Matthews’ mum.A family friend said: “If Shauna gets off manslaughter that would absolutely crush them, I know that.“I reckon it would tip them over the edge.” Duringthe pair’s trialat Bristol crowncourt, changes to the ruling were on the verge of being introduced.The judge’s biggest worry was that the Supreme Court would make their decision before the jury returned a verdict, with the case potentially starting under one ­interpretation of the law but ending under another which could have seen it derailed.Matthews and Hoare were appealing their ­convictions and sentencing before ­today’s ruling.