By Ben Jeffrey
BBC News, West Midlands
Marcus Ellis is no stranger to murder trials.
Birmingham has developed an unwelcome reputation
The 24-year-old - one of the men convicted of the killings of Letisha Shakespeare and Charlene Ellis - was cleared of the fatal stabbing of Christopher Clarke, 22, outside a Birmingham nightclub in March 2000.
That case was dropped because witnesses were not prepared to admit they saw the knife being used.
The Clarke case is one of five since 2000 involving suspected gang members, accused of using weapons to kill young men in Birmingham, that have reached court but not resulted in a conviction.
West Midlands Police have cited witness intimidation as a factor in some murder investigations.
'Curious approach to morality'
The killing of Gladstone Johnstone provides an interesting case study.
He was shot dead aged 34 in a Birmingham nightclub in March 2002, two years after he himself had been cleared of involvement in a suspected gangland murder.
The father-of-two had been accused of helping to drag Daniel Brown from the now defunct Plaza club in Handsworth, where the 20-year-old was shot three times in an execution-style killing.
The victim's brother Nigel, who was also shot but survived the attack, would not testify and Mr Johnstone walked free, cleared of murder, wounding with intent and possessing a firearm.
The judge, Mr Justice Wright, said the jury probably came to its decision as a result of "civilian witnesses" with a "curious approach to morality, to say nothing of the truth".
Victims of 'gang' murders since 2000 where the case has reached court but not resulted in a conviction
Corey Wayne Allen
Errol Robinson, a partner with Birmingham law firm McGrath & Co, who was part of Rodrigo Simms' and Ellis' defence team during the latest trial, accepts that the intimidation of witnesses has had a part to play in the collapse of other West Midlands murder trials.
But he also places some of the blame for failed prosecutions with West Midlands Police, who he says have been too prepared to rely on "dubious" witnesses in the past.
Mr Robinson told BBC News that one prosecution witness in a recent murder trial had made six or seven changes to his statement before taking the stand.
The solicitor said the witness then gave yet another version of events and was taken apart by the defence QC.
Mr Robinson also believes the will to tackle the issue of gang shootings did not exist before the murders in New Year 2003.
Errol Robinson said the killings created the will to tackle gun crime
He said: "Without them nobody would've been very bothered to deal with the problem."
But Det Chief Insp Phil Ball, from the murder investigation unit in Birmingham, is not convinced by this analysis.
"If there is (political) pressure to solve such crimes, it's very well-placed.
"It's right these people (gang members) don't see themselves as untouchable - a lot of them have been touched in the last few months."
There have been successful prosecutions in three "gangland" murder trials since 2000, and Mr Ball pointed to the force's recent success in securing four convictions in November for the murder of Daniel Bogle.
The 19-year-old was shot dead as he talked to friends in Smethwick, West Midlands, in August 2003.
The case could not be reported until the New Year shootings case ended, as one of the guilty men, Cairo Beckford, is the brother of the man acquitted mid-trial, Tafarwa Beckford.
"What we saw in the Bogle case was a lot of people giving evidence in full view in their own name. I'd call it old-fashioned evidence," Mr Ball said.
"There were threats made. There were serious and concerted attempts before the trial and during it to derail witnesses. It's something we expect.
'Gang' murder victims whose killers have been convicted this decade
"But I think that makes their testimony more powerful - witnesses who are there in spite of their fear."
Mr Ball added: "I also don't accept there's an over-emphasis on unreliable witnesses.
"The best place to test the reliability of a witness is in court. If a witness is unreliable, they should be tested there."
And so although West Midlands Police can celebrate the convictions of Ellis, Gregory, Martin and Simms, the murder of Gladstone Johnstone has not been solved.
Kirk Robinson, of Winson Green, was cleared of involvement in his shooting, on the judge's directions, in February 2003.
The case is one of several that remains open.