You can’t read Chandler v The State (Trinidad and Tobago) (No 2)  UKPC 19 without thinking of the anticipated overruling by the Supreme Court of the United States of Roe v Wade.
When will a court of final appeal overrule its own earlier decision, particularly on a point of constitutional interpretation?
The Board addressed the jurisprudence on this at -. The main points are:
Strong reasons for departure from the earlier decision are needed .
Stare decisis requires the greatest of hesitation before re-opening the issue; the earlier decision must be shown to have been wrong and lacking a sufficient foundation .
As the SCOTUS has said, a special reason for departure is needed, beyond a mere belief that the earlier decision was wrong .
It is necessary to avoid damage to the rule of law .
Something more than simply thinking the earlier decision was wrong is needed: for example it may have hampered the proper development of the law or distorted the law by being in conflict with established legal principles or by having to be distinguished in subsequent cases to such an extent that the law is uncertain .
There needs to have been a material change in circumstances since the earlier decision .
Where the court interpreted legislation, it will be more appropriate for the legislature to make the change, in contrast to common law which is more appropriately left to judges to change (citing Posner) .
The fact that the earlier decision was that of a mere majority does not weaken it, because the law has to have some way of resolving differences between judges .
Stare decisis promotes certainty, predictability, planning and the giving of legal advice .
As Lon L Fuller said, a system of legal rules has eight “desiderata”, relevantly here - retroactive laws should be avoided, legal rules should be clear, there should be a constancy of law through time, there should be correct administration of law .
I add this: Another thing lawyers can’t help thinking about in this context is the difference between the internal and the external morality of law. If conformity with the requirements of the rule of law is a matter of the internal morality of the law, does such conformity tend to serve the requirements of external morality too? The (sadly, late) Professor of Jurisprudence at Oxford, John Gardner, considered this in his Law as a Leap of Faith (2012, OUP) Chapter 8, where at 220 he concludes, “Fuller is no legalist but he is surely, on this front, a bit of a quietist. He encourages lawyers to think that they are already doing their bit, qua lawyers, to save us from the abyss so long as they are upholding the rule of law. But there is always more, and sometimes more important, work to do.”