A POLICE officer knew about crucial evidence for almost four years before it emerged to have a major murder trial thrown out.

The officer, who cannot legally be named, failed to give prosecutors evidence which pointed to the innocence of two men who were on trial for the murder of a Rebels bikie gang member, the Supreme Court heard.

The evidence only materialised after it was stolen from an unmarked police car and leaked to the men's lawyers who then subpoenaed it.

The sensational revelation saw Anthony Tan and Nathan Keith Reddy this year acquitted year over the shooting death of Edin "Boz" Smajovic at a Campbelltown workshop in January, 2009.

The Sunday Telegraph can reveal the officer in charge of the investigation became aware of the evidence on April 22, 2009, according to Supreme Court documents.

It was only given to DPP prosecutors on February 20 this year - when it was handed to them by Mr Tan and Mr Reddy's lawyers, the documents said.

The evidence was among a laptop, a USB stick and a police notebook which were stolen from an unmarked police car at Fox Studios on January 6, 2010.

Adding to prosecutors' embarrassment, Mr Tan and Mr Reddy won a costs application in the Supreme Court last Monday.

Mr Reddy's lawyer Brett Galloway said his client was considering launching a civil claim against the state.

"The police orchestrated a litany of lies to prosecute two people when they held evidence which showed they hadn't done it," Mr Galloway said.

It is understood that Mr Tan's lawyer Philip Stewart has also briefed a barrister for a similar civil claim.

Mr Tan fled to Vietnam after the shooting and was at one stage included on the NSW Most Wanted list.

In court, Justice Megan Latham said "there was a good deal of other material known to the police, and not disclosed to the DPP". The information stolen from the police car said an "Islander man", who cannot legally be named, accompanied Mr Smajovic to the workshop and confessed to "having shot someone", the court heard.

The Islander man allegedly made the admission on a mobile phone call to another person, whose name is legally suppressed, the court heard.

Police searched the Islander man's phone records which revealed the call was made at 3pm on the same day Mr Smajovic was killed, the court heard.

Further details of the note have been legally suppressed. Defence lawyers subpoenaed the information and received it on February 13.

The DPP withdrew a murder charge against Mr Tan and an accessory to murder charge against Mr Reddy on February 26. Prosecutors argued that Mr Reddy knew about the theft of the information as early as 2010.

A police spokesman declined to answer whether an internal investigation was under way.

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