Prisoners narking on each other at Otago Corrections Facility may be behind a spike in calls to an anonymous tip-off line.
The Department of Corrections introduced the Crimestoppers line on June 21, 2010 "in order to provide prisoners with an anonymous and safe way to report crime", operations assistant general manager Leanne Field said.
Between then and August this year, about 1500 calls had been made from prisons to the free reporting line, of which half came from the Otago Corrections Facility at Milburn.
Ms Field told the Otago Daily Times prisoners had a great deal of knowledge about "other criminals, previous crimes that have been committed and criminal acts that are being planned for the future".
Prisoners might know of contraband coming into the prison, hear other prisoners brag about crimes they have committed, or know an associate on the outside who is about to commit a crime.
"The fear of being labelled a 'nark' and the repercussions prisoners may face from their peers in prison, or criminal associates in the community, can prevent them from speaking up with that information."
Prisoners were encouraged to speak to staff about information they might have, but Crimestoppers gave them another option, she said.
However, she was at a loss as to why Otago Corrections Facility prisoners accounted for half of all calls to the Crimestoppers line.
"Crimestoppers information has been used to identify various forms of offending within prisons, including contraband introduction, standovers, fraud and potential escape attempts.
"While there is no known reason why more calls have been made from some prisons such as Otago Corrections Facility, it could relate to how much the number has been promoted at the site or to a small number of individuals who have made numerous calls."
Calls to Crimestoppers were free from prisoner payphones, and were exempt from telephone monitoring.
While the calls were anonymous, Crimestoppers prepared a report summarising information provided during each call. The report is then provided to the relevant authority, such as Corrections, the police or other agencies.
Corrections previously operated its own crime-reporting line, Jailsafe, with calls answered by the department's operational intelligence staff, who are charged with reducing crime in prison.
"Jailsafe catered solely for the reporting of crime within prisons. Crimestoppers provides the additional opportunity for prisoners to report crime occurring within the community, and this has contributed to the increased use by prisoners."