An investigation has started into the criminal justice failings that resulted in a bus passenger being killed by a man who should not have been released from prison.

Richard Whelan was stabbed seven times after trying to stop Anthony Joseph throwing chips at his girlfriend on the top of a double-decker bus.

Joseph had been released from a young offender institution hours before the attack, despite a warrant being in force for his arrest on another matter.

He pleaded guilty yesterday to manslaughter on the grounds of diminished responsibility, after jurors failed to reach a verdict on murder. He is being treated for paranoid schizophrenia at Broadmoor secure hospital.

Government ministers requested details of the case from its criminal justice agencies last night. A spokeswoman said: “This case shows a number of failings for the criminal justice system as a whole, which is of great concern to the Government.”

At the Old Bailey trial CCTV footage of the attack showed Mr Whelan, 28, a hospitality agent from North London, struggling with Joseph, 23, after he threw chips at his girlfriend, Kerry Barker, 38, and another woman on the number 43 bus in Holloway Road, North London.

Victor Temple, QC, for the prosecution, said: “An altercation broke out which was not between equals. The defendant, who habitually carried a knife, became verbally and physically aggressive. He took out the knife and stabbed the unarmed Mr Whelan in the top part of his body. The defendant had been drinking and taking drugs and needed little or no excuse to turn his pent-up anger against the innocent victim.”

It emerged that Joseph had been released from a young offender institution in Manchester only a few hours before the attack on July 29, 2005, after a sex allegation against him had been dropped. But he should have been detained because he was due to appear at another court for a burglary offence. Prison sources said that the institution did not know of the outstanding warrant.

He had been arrested by Merseyside Police on May 18, 2005, and charged with burglary. He was then bailed by Liverpool magistrates to his London address, subject to a curfew. But a bench warrant was issued when he failed to appear for a hearing at Liverpool Crown Court on June 27.

He had been arrested in the interim by Surrey Police and remanded in custody on June 10 by North Surrey magistrates on charges of abduction and having unlawful sex with a 15-year-old. The charges were dropped five weeks later through lack of evidence and Joseph was released from Forest Bank, a privately run young offender institution in Manchester, on July 29.

Arrangements had already been made to bring him from Forest Bank to Liverpool Crown Court for the burglary hearing on August 3. But although the bench warrant was on the Police National Computer, the prison was not aware of it. Merseyside Police were not aware that Joseph was in custody because, it is understood, the computer had not been updated.

Outside the court yesterday, Teresa Ward and Dolores Whelan, the sisters of Mr Whelan, said that they were disappointed with the verdict.

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