The Supreme Court has said judges should ordinarily follow earlier decisions made by courts at the same level and must explain why if they decide to depart from them.
Mr Justice Peter Charleton set out the principle in a concurring judgment delivered in a group of family reunification appeals concerning section 56 of the International Protection Act 2015.
The cases involved applicants identified as A, S and S, and I, with the Minister for Justice and Equality, Ireland and the Attorney General among the parties. The detailed family reunification issues were addressed in a separate judgment of Ms Justice Dunne, with which Charleton J agreed.
His judgment focused instead on what lawyers call horizontal, or co-ordinate, precedent. This concerns an earlier ruling by another judge of the same court rather than a binding decision from a higher court.
Charleton J said a judge of first instance may depart from an earlier decision at the same level, but should ordinarily follow it unless satisfied that it is wrong. Where a judge does take a different approach, reasons should be stated.
He referred to earlier authorities including Re Worldport Ireland Limited and Kadri v Governor of Wheatfield Prison. Possible reasons for departing from an earlier ruling could include an authority or legislation having been overlooked, relevant European law not being considered, or later developments changing the understanding of the applicable legal principle.
The judge stressed that explaining such disagreement is not an act of disrespect. Rather, it supports legal certainty and allows an appellate court to understand precisely why two judges have reached different conclusions.
In the appeals before the Supreme Court, Charleton J said the High Court judge, Barrett J, had carried out a rigorous analysis and had effectively revealed why he differed from an earlier High Court decision. However, the rule required the reasons for that departure to be stated expressly.
The judgment therefore clarifies how judges should deal with conflicting or potentially conflicting decisions at the same judicial level.