The country's spy agency watchdog says the SIS behaved in a "questionable" way when it decided not to tell police it knew a serious crime was being committed.
The report by the Inspector-General of Intelligence and Security comes after RNZ revealed in September that a former SIS agent made a complaint to the security watchdog after being haunted by the memory of what he found during a covert operation in the late 1980s and early 1990s.
Investigative journalist Guyon Espiner explains what happened.
