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A teenager who worked for New Zealand Post has admitted scrawling abusive messages on exam papers sent to his former high school classmates, but says it was intended only as a prank.
The person is likely to go unpunished as he left his temporary mail processing job a week before the messages were discovered, and New Zealand Post - in discussions with police - has been unable to find a legal basis for seeking a prosecution.
At least three Cashmere High School students received their NCEA papers in the mail with messages such as "Good one Dick" and "You useless sack of poo".
The former Cashmere pupil who was responsible for sorting the papers into envelopes at the Christchurch Mail Centre had recognised the names of former classmates and written the messages as a joke, said New Zealand Post postal services chief executive Peter Fenton.
"The reputation and trust we enjoy is very precious to New Zealand Post. We regard this as very serious," Mr Fenton said.
"We will have to review our processes to ensure it doesn't happen again. But we do handle 1.9 million exam papers ... and this is the first occasion in four years where we have had any matter like this. It is very much an isolated incident."
Cashmere High School yesterday said it was "extremely disappointed" over what had happened to its students, and it shared their concerns.
Sanjay Narayan, one of the students whose exam paper was defaced, told the Herald he had moved on from the incident but was glad to hear the person responsible had been identified.
He said he had suspected a former student from his school was responsible because of a nickname used in a message on an NCEA paper sent to another student.
Another targeted student, Josh Potter, said: "Now that he's been caught, there will at least be some answers to explain it. People can see the funny side of [the messages], I guess."
A New Zealand Post spokesman said discussions had been held with police about potential for charging the person responsible, but they had not been able to find an "obvious criminal act".
Under the Postal Services Act, a person can be charged for unlawfully opening a postal article, and faces up to six months in prison or a $5000 fine.
"In this case the employee was not handling mail per se, he was just sorting exam papers," the New Zealand Post spokesman said.
Senior Sergeant Neru Leifi, of the Christchurch police, said that if a complaint was received about the abusive messages on the exam papers, it would be investigated.
New Zealand Post plans to write to the targeted students to apologise for the distress caused.