Justice Hidden said the decision of the mother to plead guilty, in the face of evidence from two respected forensic psychiatrists that she was mentally ill at the time she did it, was "troubling". The mother cannot be named for legal reasons.
But he accepted an affidavit from the mother's lawyer that she had sufficient understanding of her defence of mental illness and at one stage had considered taking that course before deciding against it.
Justice Hidden, who will hear the case against the mother today, has heard evidence of her present mental state and her fitness to plead.
The psychiatrists who examined the mother were Dr Stephen Allnutt and Dr Olav Nielssen. Dr Allnutt gave evidence that she was now taking anti-psychotic medication and he could not identify any symptoms of psychosis apart from a certain "concreteness" in her thinking, which meant that she was very dogmatic and not engaging.
According to Dr Allnutt, the mother had said what she had done was "very wrong" and that, "I need to be sentenced".
She had said that she intended to plead guilty and she was not mentally ill at the time of the deed. But she had also indicated that she might not have been well at the time.
Dr Allnutt said her inflexibility was reflected in the fact that she wanted to plead guilty despite advice that the plea should be not guilty on the grounds of mental illness.
Justice Hidden said a person had the right to plead guilty despite the fact that others might question the decision.
"Presumably there are personal reasons for it," he said. "It is clear as one would expect that she is deeply remorseful for her actions. For all I know, there may be reasons for it that have not been explained.
"Further, on the material before me, there is nothing to suggest it is not a choice consciously made where other options are available to her. On material before me, it is clear that [the mother] has an insight into her mental illness."
The Crown prosecutor, Sarah Huggett, asked for an adjournment tomorrow morning for her to get instructions on how the Crown should proceed.