Assembly members have approved a statutory rule which will mean corporate manslaughter may apply to deaths in custody where there has been a "gross breach of duty of care", on 25 June 2012.
Justice Minister David Ford sought approval for the draft Corporate Manslaughter and Corporate Homicide (2007 Act) (Commencement) Order (NI) 2012.
He said it extended across the United Kingdom and would help to prevent deaths for those in custody and detention.
Mr Ford said the corporate manslaughter offence would come into effect from 3 September 2012 and would apply to those held in court detention cells, prisons, police cells, and patients detained under the mental health order.
"I hope we do not see judgements in this, but see organisations ensure that provisions are in place to ensure that deaths in custody do not happen," he added.
Deputy committee chairman Raymond McCartney highlighted that the order would focus on managerial failures and would mean a body would be prosecuted and not an individual.
The DUP's Peter Weir said he welcomed the introduction of this legal protection being put in place.