The police watchdog has also acknowledged its initial response to a complaint about the incident was unsatisfactory.
The apology, contained in a letter from Clutha-Taieri area response manager Senior Sergeant Stan Leishman, said a former Middlemarch officer returned evidence to the wrong person and police also failed to inform one of the men he had been charged with unlawful hunting.
"The standard of investigation was poor and you have quite rightly pointed out the errors made by police ... " it said.
In the November 2016 incident, the pair, and another hunting companion, were met by then Senior Constable Helen Fincham-Putter as they emerged from privately-owned forestry block after a pig hunting trip near Mt Misery, south of Milton.
Ms Fincham-Putter, who this year resigned as the sole-charge Middlemarch police officer, believing the men had been hunting in the forestry block illegally, stopped their vehicle and seized GPS units belonging to the men.
Police later initiated unlawful hunting charges against two of the men, whom the Otago Daily Times has agreed not to name, but not against the third hunter.
One of the men involved contacted Northland woman Shannon Parker, who advocates for those with misconduct complaints against police.
Ms Parker assisted him in contacting the Independent Police Conduct Authority (IPCA), questioning the legality of the search and seizure, and complaining police had held the GPS unit for a long period before it was returned, to the wrong man, after charges were dropped.
More than a year later all illegal hunting charges against both men were dropped.
In its first response to the complaint, an IPCA case resolution manager said the authority had not identified "anything of concern in relation to the conduct of the police staff involved," and no further action would be taken.
However, at the urging of Ms Parker, IPCA staff reviewed the matter and last month she was sent an email saying its initial response was "unsatisfactory".
Last week, Ms Parker received the letter from Snr Sgt Leishman, formally apologising for Ms Fincham-Putter returning the GPS to the wrong man.
"He was not the owner of the GPS unit and no arrangement had been made for him to act as an agent for [his hunting companion]."
The letter also revealed one of the men was probably not informed of the unlawful hunting charge against him because the officer failed to create the required documents.
"It is fortunate that prosecutions withdrew the charging document promptly," he said.
The standard of investigation was poor and Ms Parker had "quite rightly" pointed out the errors made by police, "in particular that of ... Helen Fincham-Putter".
When contacted, Snr Sgt Leishman said he had no involvement in the investigation and was responding after a request for further information from the IPCA. Because Ms Fincham-Putter had resigned from police there was no action police could take against her, he said.
Ms Fincham-Putter, who now runs Stanley's Hotel at Macraes Flat, said yesterday she was unaware an apology had been made. She otherwise declined to comment.
