Two of the packages were addressed to Mr Dumolo, the other to Jonathon Adams, and all were addressed to 313 Eason St, Rotorua.
Mr Dumolo actually lived at 3/13 Eason St - there was no No 313 - so Detective Karin Staunton organised her search warrants for 3/13.
A further search warrant was executed to search Mr Dumolo's bank accounts.
It was never established that the packages seized by Customs contained the synthetic drugs mephedrone and napthylypyrovalerone.
But Appeal Court justices Randerson, Hansen and Lang found this week, the warrant applications were factually incorrect in stating the packages were addressed to 3/13 Eason St. They were addressed to 313 Eason St. Having established there was no 313 Eason St and that a David Dumolo lived at 3/13 Eason St, Ms Staunton drew the obvious inference that the packages were intended for delivery to that address.
She said in evidence she decided to say the packages were addressed to what she believed to be the correct address, rather than explain why she believed that to be the case, the Court of Appeal decision said.
"This was an error of judgement on Detective Staunton's part. It was an unwise shortcut.
"The evidence available to the police did not in fact provide reasonable grounds for believing that evidence associated with the commission of an offence would be found at the premises. It did not provide grounds for believing that the substances in the intercepted packages were controlled drugs. The first warrant was accordingly unlawful and unreasonable and the second, inevitably, unlawful and unreasonable too."
The Court of Appeal quashed the convictions and said there would be no order for a retrial.
Meanwhile, Mr Dumolo was sacked from his IT job at Lakes District Health Board in Rotorua for stealing a blank DVD. It is understood his appeal to the Employment Relations Authority against the decision to sack him from the Lakes DHB was set for next month.
Mr Dumolo could not be reached for comment.