Which act legally introduced the defense of diminished responsibility in Ireland?

The defense of diminished responsibility was legally introduced in Ireland by the Criminal Law (Insanity) Act 2006. This Act amended the previous legal framework by defining diminished responsibility as a specific defense that can reduce the culpability of a defendant who suffers from a mental disorder that impairs their ability to understand the nature of their actions or to form the intent necessary for the commission of a crime. This is significant in the context of criminal law, as it allows for a nuanced approach to accountability in cases where mental health issues may affect an individual's state of mind at the time of the offense.

The introduction of this defense reflects a growing understanding of the interplay between mental health and criminal behavior. It enables defendants to present evidence of their mental state and seek a verdict that encompasses their diminished capacity rather than a straightforward plea of not guilty. This legislative shift has important implications for how justice is administered in cases involving mental health considerations.

In contrast, the other options pertain to different legislative acts that do not specifically introduce or recognize the defense of diminished responsibility in the same way. Therefore, the Criminal Law (Insanity) Act 2006 is the correct reference for the introduction of this important legal defense.