08 · Forensic psychiatry: the disorder behind the behaviour

8.1 Violence: mechanisms and risk formulation

Why this person, in these circumstances?

Previous violence shows the person's established pattern: the triggers, targets and circumstances in which harm occurred. Substance use, persecutory fear, anger, impulsivity, treatment interruption and access to weapons may reactivate it. Most people with mental illness are not violent; a diagnostic label alone explains little.

Psychosis may make an attack seem like self-defence. Other mechanisms include perceived external control or threatening commands. A command hallucination does not imply obedience: perceived power of the voice, associated beliefs and previous compliance matter. Mania adds irritability, disinhibition and grandiosity; intoxication reduces restraint. Withdrawal, delirium and brain disease can produce frightened or disorganised aggression.

Know what the instrument measures. HCR-20 V3 structures professional judgement through historical, clinical and risk-management domains. It supports a formulation and future scenarios, rather than an individual probability. PCL-R assesses psychopathic traits. Actuarial tools use predefined variables to estimate outcomes. Sexual offending needs an appropriate specialist framework, such as Static-99R, SVR-20 or RSVP.

Rapid tranquillisation

This is urgent parenteral sedation when oral treatment is unsuitable or insufficient. NICE's adult options are IM lorazepam alone or IM haloperidol with IM promethazine. Prefer lorazepam when information or previous antipsychotic exposure is unknown, or the ECG is unavailable or indicates cardiac risk.

Haloperidol can cause QT prolongation and dystonia. Benzodiazepines can suppress respiration, especially with other sedatives. Monitor consciousness, breathing and vital signs; sedated, intoxicated or medically unwell patients need more frequent checks.

8.2 Morbid jealousy: identify the form of the belief

Morbid jealousy is pathological preoccupation with a partner's supposed infidelity. Othello syndrome is the traditional name, especially for delusional jealousy. The content is similar across presentations; the form of the belief distinguishes them.

An actual affair does not settle the diagnosis. Certainty, interpretation and behaviour must still be proportionate to the evidence. Surveillance, coercion and violence remain harmful whatever the partner's behaviour.

Alcohol dependence, erectile dysfunction and relationship breakdown can reinforce one another: insecurity increases, alcohol reduces inhibition, and jealousy gives anger a target. Also consider schizophrenia, psychotic depression, mania and neurocognitive disease. New jealousy with personality change or cognitive decline raises concern for neurological illness.

Delusional disorder: ICD-11 requires at least three months of delusions, with comparatively preserved functioning outside their consequences. Exclude another disorder, substance or medical cause. Prominent disorganisation, negative symptoms or characteristic schizophrenia symptoms point elsewhere. Jealous and erotomanic describe delusional content; they are not separately coded ICD-11 subtypes.

Treatment follows the syndrome: an antipsychotic for delusional jealousy; an SSRI and appropriate psychological treatment for obsessional jealousy. Treat alcohol dependence and mood disorder as well. Evidence favouring a particular antipsychotic for isolated jealousy is limited. Avoid routine couple therapy when coercion or violence makes joint work unsafe.

Characteristic targets are the partner and supposed rival. Suicide may follow violence. Separation can intensify rejection and loss of control, so does not guarantee safety. Children may suffer directly or through domestic abuse.

8.3 Erotomania and stalking

Erotomania

Erotomania, or de Clérambault's syndrome, is the belief that another person is in love with the patient. The person may have higher status or be a briefly encountered professional. Politeness becomes a declaration; rejection becomes concealment or outside interference.

It occurs in delusional disorder, schizophrenia, mania and organic illness. Reduced need for sleep, increased energy and wider grandiosity suggest mania; a romantic theme alone does not.

Stalking motives

Stalking is repeated unwanted pursuit and often occurs without psychosis. Mullen's typology describes motives, not diagnoses or a fixed ranking of danger.

Escalation, persistence, previous violence, threats, sexual coercion, weapons and approaching the target's home increase concern. Knowledge of the person's routine facilitates access. Partners, relatives and professionals who obstruct pursuit can become additional targets.

Treat psychosis where present, alongside specialist risk management and target protection. A legal order restricts behaviour but may leave its motivation unchanged. Necessary, proportionate disclosure can be justified to prevent serious harm. Tarasoff is a US decision, not a UK statutory duty.

8.4 Fire-setting, arson and pyromania

Fire-setting is an act; arson is an offence; pyromania is a rare diagnosis. Most deliberate fires have another explanation: revenge, financial gain, concealment, suicide, communication of distress, excitement, psychosis or intoxication.

Pyromania involves repeated difficulty controlling fire-setting impulses, fascination with fire, tension or arousal beforehand, and pleasure or relief during or afterwards. Another disorder or external motive must not better explain it. Burning a building to kill imagined persecutors suggests psychosis; burning it for insurance money is instrumental.

Intellectual disability or autism may affect understanding, communication and restricted interests. Seek the function of the behaviour rather than assuming the diagnosis explains it. Childhood fire-setting may accompany conduct problems; new disinhibition may indicate brain disease.

Occupied premises, blocked escape, failure to warn and increasing fire spread indicate serious potential harm. Fascination with emergency vehicles is not reassuring. Sexual arousal linked to fire is uncommon but changes the formulation. The historical Macdonald triad (fire-setting, animal cruelty and enuresis) does not reliably predict an individual's future violence.

Treatment addresses the mechanism: psychosis, dependence, impulsivity, communication needs or the offence cycle. There is no standard medication for arson itself.

8.5 Exhibitionistic and paedophilic disorders

Interest, disorder and offence

These are separate concepts. An allegation alone cannot establish a paraphilic disorder. Someone seeking help for risky sexual interests may never have offended; an offender may lack a sustained paraphilic arousal pattern.

ICD-11 assessment considers the sustained arousal pattern, behaviour, distress and developmental context; sexual behaviour between close-age peers does not establish paedophilic disorder. Adult sexual orientation is separate from age preference. New sexual disinhibition in later life particularly suggests frontal brain disease.

OCD can produce intrusive fears of being sexually dangerous. Examine desire, arousal, avoidance, intrusive fear and behaviour together. Shame and distress occur in both presentations; one disturbing thought cannot distinguish them.

Risk and recurrence

Movement from fantasy to preparation, grooming, repeated access to a child, contact offending, sexual images of children and minimisation of harm all matter. A child's apparent compliance is not consent. Online offending can involve real victimisation.

Static-99R estimates recidivism from fixed variables in specified offender populations and requires trained use. Dynamic assessment adds sexual preoccupation, self-regulation, relationships and access to potential victims. Disclosure or arrest can also precipitate suicide risk.

8.6 Medication used to reduce problematic sexual arousal

Medication supplements psychological work on the offence cycle, distorted beliefs, emotional regulation and recurrence prevention. Selection is specialist-led and depends on formulation, severity, consent and physical health.

Cyproterone: meningioma risk rises with cumulative exposure; current or previous meningioma is a contraindication. MHRA advice limits use for severe hypersexuality/paraphilias to when other interventions are inappropriate. Check liver disease and thromboembolic history, and monitor liver function.

Triptorelin: the initial testosterone surge may briefly increase sexual drive; an antiandrogen may be considered during this phase. Long-term suppression requires attention to bone health, mood, glucose and cardiovascular risk. Severe osteoporosis contraindicates Salvacyl, whose licence requires psychiatrist-led treatment with psychotherapy. A depot injection is distinct from surgical hormone implantation under mental health law.

8.7 Fitness: which question is being answered?

The Pritchard abilities are understanding the charge, deciding a plea, challenging jurors, instructing lawyers, following proceedings and giving evidence. The clinician describes impairment; the court decides fitness. Residual hallucinations may permit participation, while a delusion that the solicitor is a persecutor may prevent instructions. Planning or concealment does not exclude psychosis.

Intellectual disability likewise does not establish incapacity, inability to parent or inability to decide about contraception. Parenting support and safeguarding address actual needs. Being next of kin does not authorise consent to an adult's sterilisation. Legal detail is in Chapter 17.