The maker of the antipsychotic medication Clozapine is investigating whether the country's only convicted plane hijacker, Asha Abdille, had an adverse reaction to the drug.
Asha Abdille, whose prison sentence ends today, stabbed both pilots and injured a passenger on an Air New Zealand flight from Blenheim to Christchurch in 2008.
The Privacy Commissioner is defending the secrecy about the case.
Last month, RNZ revealed the 42-year-old made threats to hijack another aircraft and set herself on fire.
The Somali refugee becomes a special patient on a compulsory treatment order from today, and critics argue very little will be publicly said about her risk from now on.
The Privacy Commissioner, John Edwards, told our reporter Tim Graham there's no need for the public to know about the leave she may be granted.