A TEENAGE killer heard a Cockney voice telling him to “‘do it, f**king do it’” moments before stabbing Kian Tordoff five times, a court has heard.

The 17-year-old, who cannot be named due to his age, has denied murder but pleaded guilty to an alternative of manslaughter of the 19-year-old on “diminished responsibility” on account of his mental health at the time of the killing, on John Street, Bradford, on October 2010 last year.

Dr Michael Crawford, giving evidence for the prosecution on Monday at Bradford Crown Court, came to the diagnosis of psychosis in the 17-year-old.

The jury heard one specific voice – that of a London man – had been speaking to the teenager for some time.

The 17-year-old said he grabbed a knife at home because the voice told him to protect himself, after arranging to pick up a phone from Bradford city centre that had been dropped by another defendant – Arbaz Khan – during a fight.

Dr Crawford – who interviewed the 17-year-old once - said the teenager said he got a kitchen knife as “the voice was telling me to take a knife, someone is going to stab you."

The 17-year-old also recalled hearing the voice moments before fatally stabbing Mr Tordoff.

He told Dr Crawford he blacked out during the chase but remembered the voice said: "there, that's it, do it, do it, f**king do it”.

Dr Crawford said it was “not a significant contributory factor in allegedly causing the killing of Kian Tordoff” and while he was of the opinion it did impair his rational judgement and self-control, this was not substantial.

But Dr Seena Fazel, for the defence, felt the teenager’s condition impacted his ability to form a rational judgement and to enact self-control and that it was a significant contributory factor in causing him to kill.

The other five defendants in the trial are: Arbaz Khan, 22 and Aizaz Khan, 27, both of Yew Tree Avenue in the Daisy Hill area, Amaad Shakiel, 20, of Leaventhorpe Lane, Adam Qayum, 23, of Avenel Road, Allerton and Mohammed Adil Hussain, 18, of Kite Mews, Lower Grange.

All men deny murder and the attempted murder of Matthew Page – known as Matthew Lowther – who was stabbed twice.

They all also deny a third count – wounding with intent - in relation to Mr Lowther.

The 17-year-old denies that too but pleaded guilty to unlawful wounding instead.

The trial continues.