Ministry of Justice figures show that 18 to 25-year-olds account for a third of the total social and economic costs of crime as victims or offenders, despite making up only 10 per cent of the population.

This age group also accounts for 20 per cent of the prisoners who self-harm, although they represent only 12 per cent of the prison population.

Young adults should be recognised as a distinct cohort in the eyes of the law. Separate courts should be used and sentencing principles formulated for them that adequately take account of developing maturity.

There is now a wealth of scientific evidence to support what we have always known: that young people do not magically turn into right-thinking mature adults at midnight on their 18th birthdays. Their brains continue to develop and they do not achieve the minimum level of developmental maturity we would expect from an adult until they are at least 25.

Societal structures also militate against achieving full adulthood at 18. The vast majority remain dependent, living at home, through a period of transition. Their efforts towards independence and the mistakes they make require a more nuanced response when these rub up against the criminal justice system.

Since 2011, adult sentencing guidelines have stated that consideration should be given to “lack of maturity” as a potential mitigating factor.

We have seen judgments acknowledging young adults’ continued lack of maturity. For example, Lord Burnett of Maldon, the lord chief justice, said in his ground-breaking decision last year in R v Clarke that it was right to take a “child-centred” approach to sentencing, recognising the scope for rehabilitation.

While there have been small steps in the right direction, separate robust sentencing guidelines for young adults are the only way to guarantee that these important matters will always be taken into account.

Every decision regarding a young adult should take into account their developmental maturity and acknowledge that most young adults who are provided with support and opportunities to change their behaviour do just that. It is usually only a matter of time.

The police and Crown Prosecution Service should be required to assess maturity at the time of the alleged offence when determining whether to charge.

If a charge is necessary, a court should have the option of deferring the prosecution, not just the sentence. A welfare-based “young adult court” could supervise the process and be best-placed to encourage and reward progress or provide a punitive response if necessary.

This could avoid a young person’s mistake becoming an indelible conviction that thwarts their education and job prospects. It will also go some way to preventing the negative effects of custody for young adults and for the community, as demonstrated by the high number of self-inflicted deaths by young adults in custody and the extremely high reoffending rates among this age group.

We owe it to the next generation and to ourselves to do better.

This article first appeared in The Times Brief on 22 May 2019.