A police error in taking a DNA sample seven years ago has created a hurdle in prosecuting a serious assault involving two tomahawk-wielding men years later.
The assault involved a raid on a house in Christchurch by two men armed with a tomahawk.
But the Court of Appeal has ruled DNA taken from the Christchurch case cannot be used.
That is because the sample it was matched against was improperly taken in the first place, according to a judicial ruling upheld in the Court of Appeal.
The case began with the arrest of 17-year-old Ian Toki in Kerikeri in 2011, on a charge of taking a car.
A swab from his mouth was taken for DNA records at the time.
But the Court of Appeal has upheld lower court rulings that the DNA sample taken at that time was obtained in a defective manner.
That is because the police used the wrong form and because Mr Toki was not told about the rights he had to refuse consent for his DNA to be stored and used.
These relate to the seriousness of the changes against him.
In subsequent years, Mr Toki was prosecuted several times, for burglary and driving offences.
In 2015, a serious assault occurred in Christchurch, involving two men armed with a tomahawk.
In its ruling, the Court of Appeal said they were looking to buy cannabis, which was refused, and then the pair destroyed a table and stole cellphones.
The court said the principal offender then assaulted three of the occupants with varying degrees of severity.
Apart from punching them, he struck one in the head with a frying pan.
The court said a man identified by witnesses as Mr Toki was later seen drinking beer and his DNA was found on the bottle.
But Justice Harrison said that DNA could not be used, because Mr Toki had not given informed consent to the original DNA sample four years earlier, so the later DNA could not be legally matched against it.
“We acknowledge that the alleged offending is serious, the evidence is of a high quality, and that the prosecution will likely fail without Mr Toki’s 2011 bodily sample,” Justice Harrison wrote.
“However, an effective and credible system of justice will not tolerate lightly the reliance of the police on the DNA profile databank if the underlying sample was taken contrary to clear legislative prescriptions and in abrogation of the person’s rights.”
Justice Harrison went on: “It is trite that DNA is not a mere fingerprint: it contains a wealth of genetic information about a person with unlimited future utility.
“The one-off intrusion of the procedure thus permanently erodes Mr Toki’s privacy and freedom, which would usually remain beyond the reach of the state apparatus.
“Without Mr Toki’s informed consent, the bodily sample now stored on the DNA profile databank was obtained in serious, permanent and ongoing breach of his rights.”