A teenager serving a life sentence for murdering a doorman has had his conviction overturned.

Robert Tate, now 18, of Firle Road, Seaford, was convicted of murdering Justin Martin in a street brawl in Northampton last October.

Lord Justice Kay, sitting in the Criminal Appeal Court in London with Mr Justice Silber and Judge David Mellor, ruled the conviction was "unsafe" yesterday.

He said this was because of flaws in Judge Francis Allen's directions to the jury on the issues of good character and self-defence at the Northampton Crown Court trial.

But Lord Justice Kay said it was "unhesitatingly in the public interest" for Tate to stand trial again for Mr Martin's murder.

The trial will take place at a different court because of the publicity the case has attracted.

After a five-day trial, Tate was convicted of killing Mr Martin, 24, with a single stab wound in the early hours of March 6 last year.

Tate said he stabbed Mr Martin in self-defence after the doorman became involved in a heated argument with his girlfriend.

Lord Justice Kay accepted submissions from Tate's barrister, Alan Tyrrell QC, that the jury should have been instructed how to deal with evidence that the killing occurred in the heat of the moment.

Mr Tyrrell said: "We think that if ever there was a case which required the specific warning to which we have referred, this was such a case."

Mr Tyrrell had also complained that the teenager's credibility had been undermined by the judge's comments that he had not been in trouble "so far as the criminal courts know".

Lord Justice Kay told the court: "In a case where there is also positive evidence of the good character of an accused person, we think that is particularly unfortunate."

He said the flaws in the judge's summing up to the jury combined to make his murder conviction unsafe.

Tate remains in custody but his lawyers are expected to apply at Birmingham Crown Court within the next two months for his release on bail, pending his retrial.