The trial at Belfast Crown Court began on 9 September and lasted four weeks.
The prosecution's case against Mr Ward, of Colinmill, Poleglass, was based on circumstantial evidence.
The gang that robbed the bank had such detailed knowledge about its security procedures that detectives believed they had an inside man.
Mr Ward's family was one of those taken hostage by the gang, but police believed the 26-year-old had been a willing accomplice.
A key part of the prosecution case was a claim Mr Ward had made a last-minute change to the work rota to ensure he was on duty to facilitate the robbery.
However, during the trial it emerged that dozens of people could have known the identities of keyholders who had access to the bullion room where the money was stored.
On Thursday, prosecution counsel Gordon Kerr QC said the case had been brought before the court based on circumstantial evidence.
"An essential strand related to the circumstances in which the defendant came to be on the rota of the late shift of the Northern Bank on the day of the robbery.
Chris Ward, pictured walking out of Belfast Crown Court on Thursday
"(It was) fundamental in the case to the prosecution inviting the court to draw inference from other parts of the case."
He added that differences had arisen during the trial around the rota which prompted the rethink.
"Having considered the remaining evidence and the advice of counsel... it has been concluded that it would not be proper to make further submissions."
Mr Justice McLaughlin told the packed court that the Public Prosecution Service's decision to offer no further evidence was "fully justified".
He said the "audacious" robbery had been meticulously planned.
"The community should understand this is far from being a victimless crime. Those caught up in it are still traumatised by it almost four years later and for some, their livelihoods and careers are shattered," he said.
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