Another blog on request: this time from an AMHP who wants to give advice to others about the interface between assessment under the Mental Health Act 1983 and decisions in criminal law to prosecute an offender.  This dilemma presents most acutely in police custody when someone has been arrested for an offence and then assessed under the MHA.  How do you decide what to do at the end of the MH and the CJ process and quite crucially, whose decision is it as to whether the MHA or a potential prosecution take priority in any particular case?

Firstly, we need to remember that assessment of MHA admission and assessment of criminal evidence is entirely separate.  They obviously coincide or overlap in the kind of custody scenarios we’ll consider here, but they do always remain separate legal considerations.

  • Does this person meet the criteria for compulsory admission to hospital under the MHA?
  • Is there sufficient evidence to charge the person with an offence — and is it in the public interest to do so?

Early in my career, I thought the first question negated the second: that someone who is ‘sectionable’ could not be prosecuted.  I kept hearing more experienced and more senior officers talking about people having or not having “capacity” and it can become confusing.  Early on, I saw several people who were quite unwell, “sectioned” after arrest for a serious criminal offence and that was the end of that.  No legal process at all and my curiosity about all of this was the basis of my thesis when I did my criminology and criminal justice master’s.

We treat MHA admission as a proxy determinant for criminal prosecution – and we really shouldn’t.  The easiest thing to do is put that from your mind entirely and remember what the law says whilst considering the nuance and the complexity of someone’s situation when they have offended whilst seriously unwell.


As a starter for ten: nothing in law prevents the investigation, prosecution and conviction of someone who, from the point of the offence commission to the point of conviction in a criminal court, is mentally ill to a degree that means they could be detained or “sectioned” in hospital.  Whether you investigate, prosecute and convict someone who is so unwell is an entirely different matters, but proper consideration of these things starts with remembering this.  The presumes that everyone is sane and liable for their actions, unless the contrary is proved in court –  the presumption of sanity is important to remember.

It is equally true to point out that nothing in law mandates the investigation, prosecute and conviction of someone who has offended — and all cases should turn on their merits.  This is where the so-called “public interest test” kicks in: is it really in the public interest to criminally prosecute a seriously unwell person whose offence is to steal a couple of pounds worth of food, whilst they were psychotic or delusional, when admission to hospital stands a very good chance of getting them the support they need?

It may be that the risk of future offending is addressed by care and support in hospital, then community mental health care later and if that’s the judgement of those involved, why would we prosecute the offender who needs to be “sectioned”?  But if the offender who stole the low value foodstuffs had stabbed the security guard in the course of the theft, that’s a different matter entirely.  There may be far more public interest in a prosecution, even if the offender is “sectionable” because it involves serious injury with a bladed weapon.

As a general rule, the more serious the offence and / or risky the background of the offender, the more likely it is to be in the public interest to prosecute for the alleged offence.


Of course, communication is key in all of this.

  • AMHPs shouldn’t assume that prosecution can always occur or that it may immediately occur — sometimes the evidence just isn’t there (yet), no matter how serious the allegation which justified arrest.
  • Police officers shouldn’t assume that someone who is “sectionable” must be diverted from justice under the MHA and that medical factors prevent prosecuted now or later – sometimes, MHA admission is for assessment (under s2 MHA) only.
  • Everyone should talk to each other!

Most offenders arrested for less serious offences, like theft or public order offences, etc., will be diverted from justice.  Public policy has pushed in that direction for decades.  But those offenders who are alleged to have offended much more seriously need greater, deeper consideration and that means communication and taking in to account background factors.  AMHPs who judge a person “sectionable’ should seek to understand the evidential pressures on the police – is there evidence to charge or not?  The fact someone has been arrested for something serious, doesn’t mean prosecution can always occur.

I’ve told this story before: but a man was arrested for murder many years ago after he was found in a house where the body of a missing person was found.  Long story made short, he had killed her and buried her body beneath floor boards whilst seriously ill.  But in the circumstances of the body’s discovery, it was not yet known how she died and there was another man in the house at the time, also arrested.  When both men were in police custody, MHA assessment took place on one of the suspects and he was seriously unwell but there was reluctance to “section” him because he’d been arrested for murder.  The problem was, there was no evidence to prosecute him for that at the point the AMHP became able to make an application to hospital – the body had not yet been moved from its location, the post-mortem to determine a cause of death had not occurred and there were lots of ongoing enquiries required to investigate the circumstances.

In that case, the man was “sectioned” first and once the outstanding enquiries were completed, he was charged with murder whilst in hospital.  This case is not an isolated example.


We also see immediate prosecution in some cases:  you may remember some years ago, there was a bladed attack on a musician at Leytonstone Underground station just prior to Christmas?  The offender in that case was arrested, assessed in custody under the MHA and he required admission, but because of the evidence in that case, he was immediately prosecuted and brought before the courts.  After his first Crown Court appearance, he was remanded to hospital for assessment and psychiatric reports.  The same thing happened to the offender in Harrow who stabbed some Metropolitan Police officers in 2014?  << Check detail.

So it’s important the AMHP and custody officer understand each other’s outcome.  No point the custody officer seeking to divert somebody for a minor offence is the AMHP is saying the person does not meet the threshold to be “sectioned” – it may be that an out-of-court disposal would be appropriate, but it will be a CJS decision, either way.  It’s no good AMHPs hoping offenders will be prosecuted if the custody officer (or the CPS) are saying there is not enough evidence to charge, as was the case above where a body was recovered beneath floorboards.

That’s where there needs to be flexibility and understanding based on communication: what happens for example if the person does not meet the threshold for admission and there is not enough evidence to charge?


Some cases are more clear cut than others – your non-violent shoplifter who is seriously ill: no real difficulty there, is there?  Minor offence, seriously ill – diversion is highly likely.  Your very violent offender who is seriously ill: again, not always difficult.  Serious crime (and evidence to charge), seriously ill – prosecution is highly likely, but it’s not obligatory.

In cases in the middle order of seriousness, it may be that background factors are relevant to discussions between AMHPs and custody officers about which way to proceed.  Imagine something where on the face of the current incident, you may be incline to divert someone from justice – would it change your thoughts if you knew that on previous hospital admissions (which may themselves have been diversions) the person absented themselves from the hospital and was reported missing as an AWOL patient?  What is the utility in diversion, if the person then runs off and doesn’t engage?  Such background factors may cause you to go against your first instinct based only on the offence under investigation and the assessment outcome.

Equally, just because someone has been arrested for something serious and there is evidence to charge, doesn’t mean that must be the way forward.  If the AMHP knows the person can be admitted to a secure mental health bed in a medium secure unit, for example, it may be that diversion is the appropriate approach to begin with, whilst the investigation carries on.  The man who killed Christina Edkins was diverted first to a medium secure hospital and charged with her murder the following week, by way of example.

It’s just about AMHPs and police having detailed discussions about what is possible in either system and thinking together about how best to proceed in the particular circumstances and remember what Professor Jill Peay said in her 2010 book “Mental Health and Crime”: this work, at the interface of the mental health and criminal justice systems is the most complicated that any professional in these professions will do.  I couldn’t agree more – but it’s far easier if done with discussion and cooperation.

Winner of the President’s Medal, the Royal College of Psychiatrists.

Winner of the Mind Digital Media Award


All opinions expressed are my own – they do not represent the views of any organisation. (c) Michael Brown, 2023

I try to keep this blog up to date, but inevitably over time, amendments to the law as well as court rulings and other findings from inquests and complaints processes mean it is difficult to ensure all the articles and pages remain current.  Please ensure you check all legal issues in particular and take appropriate professional advice where necessary.

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