Juries Act 1981, ss 7, 8
Some people who have been convicted and sentenced in criminal cases can’t serve on a jury, namely:
people who have ever been sentenced to a jail term of three years or more, or to preventive detention
people who, in the last five years, have been sentenced to a jail term of three months or more or to corrective training.
The following kinds of people are also disqualified from jury service:
members of Parliament
people involved with the justice system, such as judges and Justices of the Peace, practising lawyers, police officers, prison officers, probation officers and people employed in the Ministry of Justice, the Department of Corrections or other prison management groups
people with an intellectual disability.