High Court: Provision for ‘reasonable mistake’ defence in child sexual assault cases declared unconstitutional

High Court: Provision for 'reasonable mistake' defence in child sexual assault cases declared unconstitutional

The High Court has ruled that a key provision of legislation related to prosecutions of child sexual assault cases is invalid under the Constitution.

The plaintiff challenged the constitutionality of section 3 of the Criminal Law (Sexual Offences) Act 2006, which provided that the “reasonable mistake” defence as to the age of a complainant was to be proved on the balance of probabilities.

Delivering judgment in the case, Ms Justice Siobhán Stack held that the provision placed a legal burden on the accused which offended his right to a fair trial and infringed the presumption of innocence in criminal cases. The court held that the provision allowed the plaintiff to be convicted even if there was a reasonable doubt as to the age of the victim.


The plaintiff was previously convicted of an offence contrary to section 3 of the 2006 Act, which criminalised any sexual act with a child below the age of 17. The plaintiff was 19 years and four months old and the victim was 15 years and 10 months old at the time of the offending. The plaintiff was sentenced to one year and ten months’ imprisonment.

Subsequently, the plaintiff issued plenary proceedings challenging the constitutionality of section 3(5) of the 2006 Act and, therefore, his conviction. Section 3(3) provided that it was a defence for a person to be “reasonably mistaken” that a child had attained 17 years at the time of the offence. Section 3(5) provided that the standard of proof that an accused was reasonably mistaken was “that applicable to civil proceedings”. Both sides agreed that this standard meant the balance of probabilities.

Accordingly, the plaintiff submitted that section 3(5) infringed his right to a fair trial under Article 38.1 of the Constitution because he was liable to be convicted on a standard lower than beyond reasonable doubt. Further, it was submitted that the section reversed the onus of proof for establishing a reasonable mistake onto the plaintiff, which created an unjustifiable legal burden on the plaintiff.

The State submitted that the section was proportionate having regard to the objective which was pursued under the legislation (being the protection of children). It was also submitted that the “reasonable mistake” defence was something that was solely in the mind of the plaintiff and therefore it was reasonable to impose an evidential burden on the accused to prove his mistake.

The State also submitted that the “reasonable mistake” defence was brought into Irish law following the landmark ruling in C.C. v. Ireland [2006] 4 IR 1, which created a constitutional crisis relating to sexual offending against children. The State pointed to reports from Oireachtas Joint Committees which provided detail on the legislative response to the case.

High Court

Ms Justice Stack began by explaining the important difference between a legal burden and an evidential burden. It was held that a legal burden was the standard fixed on a party to satisfy a trier or fact as to the existence of a fact or matter, while an evidential burden was borne by the party who contended that a particular issue should be put before the trier of fact. The evidential burden was discharged adducing sufficient evidence that a trial judge was satisfied that it should be left to a jury for consideration (The People (Director of Public Prosecutions) v. Forsey [2019] 2 I.R. 417).

The court went to consider the constitutional protection for the presumption of innocence. It had previously been determined that only an evidential burden could be placed on an accused and that the legal burden of proof always rested with the prosecution (see The People (Director of Public Prosecutions) v. Smyth [2010] IECCA 34; The People (Director of Public Prosecutions) v. Heffernan [2017] 1 I.R. 82; and Forsey).

It was also held that in Heffernan that the prosecution carried the legal burden of proving the constituent elements of the relevant offences. Further, in considering whether the presumption of innocence applied to any particular issue, a court will look at the substance of the offence and its constituent elements rather than the drafting of the legislation.

In Forsey, the Supreme Court emphasised that a reverse onus of proof on a defendant to disprove a core element of an offence would be contrary to Article 38.1 of the Constitution. As such, Ms Justice Stack held that section 3 could only place an evidential burden on the plaintiff to create reasonable doubt in the minds of jurors as to his guilt.

The court held that this issue of reasonable mistake was a core issue which related to an offence under section 3 of the 2006 Act (Heffernan). Although referred to as a defence, the issue of reasonable mistake was a “critical component” to establishing guilty, having regard to the ruling in C.C. v. Ireland. Accordingly, the presumption of innocence applied to the question of reasonable mistake and was a matter for the prosecution to prove.

Turing to consider the proportionality of section 3(5), the court held that the question was “whether the presumption of innocence, that is, the requirement that the prosecution prove guilt beyond a reasonable doubt, is a component part of a fair trial which can be legitimately restricted without compromising the overall fairness of the trial”.

Applying Hardy v. Ireland [1994] 2 I.R. 550, the court held that “the presumption of innocence is of such fundamental importance to the fairness of a trial that it is not subject to proportionate restriction as are individual rules of evidence relating to admissibility, the drawing of inferences or reverse onus provisions”. Further, the court stated: “Put simply, a trial which permits conviction where there is a reasonable doubt as to the guilt of the accused is not a fair trial.”

The case law made it clear that the constituent elements of an offence had to be proved by the prosecution and section 3(5) placed a legal burden on the plaintiff which breached the presumption of innocence.

The court accepted that it was a desirable public policy to protect children from sexual abuse. However, the legitimate objective of the legislation was determined to be the narrower objective of adducing evidence which might be very difficult to tender since it related to the knowledge of the accused.

It was noted that, on the State’s submissions, other offences such as murder or rape could also fall into this legitimate objective. If this were the case, it would “entirely hollow out the presumption of innocence”. While it was acceptable to place an onus on the accused to adduce evidence of his “reasonable mistake”, it was not acceptable for that to become a legal burden of proof, the court said.

Ms Justice Stack determined that, while there was obvious value in the Joint Committee Reports on the formulation of legislative responses to C.C. v. Ireland and the decision to not have a referendum, the courts were not obliged to defer to these views where the fundamental trial rights of an accused were affected.

The court stated that: “It is difficult to avoid the impression that subs. 5 was included simply to make it more likely to get a conviction” in child sexual assault cases. The court held that the section went further than necessary to deal with the difficulties raised by the “reasonable mistake” defence and was therefore disproportionate.


The court determined that it was a matter of fundamental fairness that an accused should not be convicted if there was reasonable doubt as to guilt. Section 3(5) of the 2006 Act dealt with the core issue of the moral culpability of the plaintiff and placed an obligation on him to prove on the balance of probabilities that he was not culpable.

This was contrary to Article 38.1 of the Constitution and breached the plaintiff’s right to a fair trial. Accordingly, the court took the preliminary view that section 3(5) should be declared invalid, but would hear from the parties on the exact form of order.

C.W. v. The Minister for Justice and Equality and Ors. [2022] IEHC 336

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