Under the Supreme Court Act 1981, section 31(3), to be entitled to apply for judicial review, a person or entity must have a "sufficient interest" in the decision being challenged. This principle, often referred to as "standing," requires a direct, personal interest in the decision or action under challenge. Trade unions and similar organisations, which represent individuals who may be affected by a decision, can have sufficient interest to challenge a policy or decision on behalf of their members. In this scenario, the trade unions represent members who are potential victims of crimes of violence and are directly impacted by the modified scheme of criminal injuries compensation. Therefore, the unions have standing to challenge the new scheme. 

Key Point: The concept of standing in judicial review cases is interpreted liberally to allow organisations representing affected individuals to challenge decisions that impact their members, provided they have a direct and personal interest in the decision under challenge.