Although there is as yet no Sentencing Council guideline setting out overarching principles in relation to the sentencing of offenders with mental health conditions and disorders, the mental health of the offender is a factor which sentencers are required to consider at Step 1 or Step 2 of the process set out in offence-specific guidelines when assessing culpability and harm and any aggravating or mitigating factors. Furthermore, the general overarching principles guideline, which provides guidance on the approach to be taken where there is no definitive guideline specific to the offence under consideration, identifies mental disorder or learning disability as a factor reducing seriousness or reflecting personal mitigation. In relation to young offenders, the overarching principles guideline to sentencing children and young people states that, as part of its duty to have regard to the welfare of the young offender, the court should ensure it is alert to any mental health problems or learning difficulties/disabilities.

Mental health conditions and disorders may be relevant to sentencing in a number of ways. (1) They may be relevant to the assessment of the offender’s culpability in committing the crime in question. Where an offender suffers from a mental health condition or disorder, the sentencer must consider whether it affected culpability. Where the offender’s mental condition has been exacerbated by a failure to take prescribed medication, or by “self-medication” with controlled drugs or alcohol, the sentencer will consider whether the offender's conduct was wilful or arose, for example, from a lack of insight into his condition. When considering matters of this nature, the sentencer will be focusing on the offender’s mental health at the time of the offence. (2) They may be relevant to the decision about the type of sentence imposed, in particular a disposal under powers contained in the Mental Health Act 1983. Where a custodial sentence is necessary, mental health conditions and disorders may be relevant to the length of sentence and to the decision whether it can properly be suspended. In these respects, it is the offender’s mental health at the time of sentence, rather than at the time of the crime, which must be considered. (3) They may be relevant to an assessment of whether the offender is dangerous within the meaning of the Criminal Justice Act 2003. (4) They may need to be taken into account in ensuring that the effect of the court’s sentence is clearly understood by the offender and in ensuring that the requirements of a community order or an ancillary order are capable of being fulfilled by the offender.

The court will be assisted by a pre-sentence report and, where appropriate, medical reports (including from court mental health teams) in assessing the degree to which a mental disorder or learning disability has reduced the offender’s responsibility for the offence, and any effect of the mental disorder or learning disability on the impact of the sentence on the offender. Difficulties may arise because there is nothing particular which prompts consideration of whether a mental health condition or disorder may be relevant to sentence. Both practitioners and judges should be alive to that possibility in adult offenders and, as with all matters of case preparation, early identification of the real issues is important. So far as children and young persons are concerned, in accordance with the overarching principles guideline to sentencing such offenders, where a serious offence has been committed by a young offender, both the court and those representing him must be alert to the possibility that mental health may be a relevant feature of the case. The younger the offender, and the more serious the offence, the more likely it is that the court will need the assistance of expert reports. Where reports obtained post-conviction reveal features of the offender’s mental health which are relevant to sentence but which conflict with the case which the offender had advanced at trial, then, in accordance with established principles, the sentencer should, while remaining true to the jury’s verdict, form his or her own view as to the proper basis for sentence.

It follows that sentencing an offender who suffers from a mental disorder or learning disability necessarily requires a close focus on the mental health of the individual offender (both at the time of the offence and at the time of sentence) as well as on the facts and circumstances of the specific offence. In some cases, the fact that the offender suffers from a mental health condition or disorder may have little or no effect on the sentencing outcome. In other cases, it may have a substantial impact. Where a custodial sentence is unavoidable, it may cause the sentencer to move substantially down within the appropriate guideline category range, or even into a lower category range, in order to reach a just and proportionate sentence. A sentence or two in explanation of those choices should be included in the sentencing remarks (paras 8–21).