The answers of Mr Burgess under cross-examination at times conflicted with his earlier evidence and also his testimony at a previous trial of Dunn on the same charge, where a jury could not reach a verdict.
Following the discharge last month, senior Crown prosecutor Scott McColgan wrote to the judge asking for a transcript of the trial to be released to the police for an internal investigation.
He said it was clear the evidence of Mr Burgess was "incorrect in material respects" and there was a "credible risk of cross contamination of a DNA match".
The application was supported by Mr Krebs, who wrote that it was "important that this matter is properly investigated by the police" and the transcript was released.
Detective Inspector Greg Cramer, of the Waitemata district, confirmed an internal investigation was "immediately launched into the matter".
"The objectives of the investigation include identifying how this occurred, and whether any processes need to be changed in order to prevent this from happening again."
The discharge of Dunn means that no one was held accountable for the 1kg of methamphetamine - with a street value of $1 million - found inside the West Auckland clubrooms of the Head Hunters gang in May 2011.
Ten other patched members were charged with possession of methamphetamine for supply but the charges later dropped as their mere presence in the clubrooms was not sufficient evidence to prove the charge.
The 49-year-old Dunn, who is the president of the West Chapter of the gang, has a criminal history dating back to 1981 including previous prison terms for methamphetamine convictions.
At one point, a police call-taker with access to the national intelligence system was leaking sensitive information to help him avoid arrest until she was caught in 2006.
Dunn is currently serving a three year sentence for the possession of 15g of P which was found discovered in the same raid on the gang-pad in May 2011.
The Armed Offenders Squad pretended to be delivering alcohol as a ruse to gain access to the gated premises on View Rd in Henderson, before sweeping through the address and arresting those inside.
The balaclava-clad officers found Dunn coming from the direction of the women's toilets outside the main building.
There, a specialist search team later discovered a motorcycle "tank bag" carrying two containers holding nearly 1kg of methamphetamine between them.
Also in the "tank bag" was a drink bottle which the police claimed had Dunn's DNA on the lid.
A second "Pak Lite" bag found in the bar contained a phone and bank cards owned by Dunn, as well as the smaller 15g container.
Senior Constable Jason Burgess told the court of the steps he took to prevent the risk of cross-contamination between items in the two bags, including changing gloves regularly and the order in which he handled the exhibits.
But under rigorous questioning from Mr Krebs, he was forced to concede his earlier assertions were incorrect.
How the case unfolded
May 2011: David Dunn and 10 other Head Hunters charged with possession of nearly 1kg of methamphetamine for supply after a raid on the West Auckland gang-pad. Dunn also charged with possession of 15g of P.
May 2012: Charges against the 10 gang members dropped as Crown could not prove direct link to the drugs cache.
September 2013: Dunn sentenced to three years in prison for possession of 15g of methamphetamine for supply. Jury unable to reach a verdict on the 1kg charge, so a second trial is ordered.
June 2014: Dunn discharged at retrial after concerns over DNA evidence. No one convicted over $1 million of P.
