A ruthless armed robber who shot dead an innocent bystander following a raid at a Birmingham building society must remain in prison for at least 27 years.

Lynton Fletcher was jailed for life last month after being convicted of the murder of Joseph Nwabuko during a string of raids in which seven other people were also shot.

Setting the minimum term before he can be considered for parole, Mr Justice Ouseley told Fletcher at Birmingham Crown Court yesterday that Mr Nwabuko's death was "completely unnecessary".

The court was told Fletcher fired a single shot which passed through the arm and into the lungs of his victim. He was convicted of murder on November 8 by a 10-2 majority verdict following a six-week trial at Birmingham Crown Court.

"You were an active participant in the robbery. This was a sophisticated, planned robbery. Carrying real and loaded firearms was part of that plan, as was the use of tracking devices," the judge told Fletcher.

He said Mr Nwabuko, from Walsall, was perhaps a naive man who saw the gang going back to their car and followed them, possibly to see what was happening or because he knew what was going on was wrong.

The judge said he was satisfied Fletcher had been the one who had shot Mr Nwabuko.

He added: "There was a deliberate returning to deal with Mr Nwabuko, a young man, alone, who offered no provocation or other reason for him to be shot than that he was there and somebody who might be able to identify the robbery gang.

"It was completely unnecessary."

As well as the murder charge, Fletcher, 27, of Little Francis Grove, Nechells, was found guilty of a charge of conspiracy to rob.

He was part of a gang which carried out a robbery spree across the Midlands in which guns were regularly carried, used to threaten, hit and shoot guards and members of the public. There were at least 19 offences committed across the region in 2003, 2004 and 2005 which netted the gang about £350,000.

The court heard how on February 9, 2004, Fletcher had been one of three men who had tracked a Securicor van to the Nationwide in the Bullring before breaking in to the building society and taking £7,000.

Timothy Spencer QC, prosecuting, told the trial that the ruthless and unnecessary use of firearms - which were discharged even after cash had been handed over - was a hallmark of the gang.

Describing Mr Nwabuko's death as cold and cruel, the QC suggested Mr Nwabuko might have been trying to foil the raiders when he was killed. He said during the robbery spree the gang had targeted cash in transit vans and had shot a number of people including a retired police officer who suffered life-threatening injuries.

David Nathan QC, defending, said there had been no intention to kill when Mr Nwabuko was shot.