Define delusion, hallucination and illusion. Classify mental illness and describe the examination of a person of unsound mind.

Definitions

• Types of delusion and their forensic importance — persecutory (that one is being followed, poisoned or plotted against) is much the most dangerous, since the person may attack the supposed persecutor and the act appears purposeful and planned; grandeur; reference, that ordinary events refer to oneself; infidelity (the othello syndrome), a delusion of a partner’s unfaithfulness which is a recognised cause of homicide of the spouse; nihilistic (COTARD), that one is dead or has no organs; hypochondriacal; of control or influence, that one is being controlled by an external agency; of poverty and of guilt, associated with depression and with suicide and extended suicide; and erotomania (de Clerambault syndrome), a delusion of being loved by another, associated with stalking
• Types of hallucination — auditory, the commonest, characteristic of schizophrenia, and dangerous where the voices are commanding; visual, which points to an organic state — delirium, delirium tremens, drug intoxication and epilepsy; tactile, classically formication, the sensation of insects crawling under the skin, in cocaine and alcohol withdrawal; and olfactory and gustatory, which suggest temporal lobe epilepsy or an organic lesion

Classification of Mental Illness

• The psychosis-neurosis distinction is what matters forensically, because insight — the awareness that one is ill and that one’s experiences are abnormal — is the faculty on which responsibility and capacity depend. A person with a neurosis knows their fear is irrational; a person with a psychosis does not know their belief is false

Examination of a Person of Unsound Mind

• Consent and capacity — capacity is presumed under the Mental Healthcare Act
• obtain consent, and where capacity is lacking involve the nominated representative → history from the person and, separately, from an informant — a relative, employer or police officer — since the person may have no insight and the informant history is often the more reliable → Detailed personal, family, medical and drug history, including alcohol and substance use, head injury, epilepsy and previous psychiatric illness → general physical and neurological examination — which must never be omitted, since an organic cause is the finding that changes everything → mental state examination — appearance and behaviour
• speech
• mood and affect
• thought (form and content, including delusions)
• perception (hallucinations and illusions)
• cognition — orientation, attention, memory and intelligence
• insight and judgement → investigations — blood glucose, electrolytes, calcium, renal, hepatic and thyroid function, vitamin B12, a drug screen, and imaging or an electroencephalogram where indicated → observation over a period, preferably as an inpatient, by nursing staff as well as by the doctor — which is how feigned illness is detected → Opinion by a board in medicolegal cases, recorded with reasoning

Distinguishing the Key Symptoms

Applied Aspects

• Always examine physically and investigate for an organic cause; hypoglycaemia, hyponatraemia, hypoxia, sepsis, drug intoxication and withdrawal all present as acute psychiatric disturbance and are reversible, and missing them is the commonest and most dangerous error
• Judge a belief against the person’s cultural background; a belief in spirit possession or witchcraft may be entirely normal in the community and is not a delusion, and treating it as one is both wrong and disrespectful
• Take a history from an informant separately; the person may lack insight, and the account of behaviour over time is what establishes the illness
• Assess insight explicitly and record the answers verbatim; it is the faculty on which every legal question in this chapter turns
• Look for command hallucinations and persecutory delusions when assessing risk; these are the features associated with violence, and a general impression of "psychosis" is not a risk assessment
• Observe over time rather than deciding at one interview; both genuine illness and feigning declare themselves through sustained observation and rarely at a single examination
• A delusion is judged against culture, an obsession against insight, and an illusion against the stimulus that produced it
• Persecutory delusions carry the violence risk, and command hallucinations carry it further; ask about both specifically
• Othello syndrome kills spouses and erotomania produces stalking; both are delusional disorders with the personality otherwise preserved
• Formication points to cocaine or alcohol withdrawal, and olfactory hallucination to temporal lobe epilepsy
• Intellectual disability is excluded from the Act definition of mental illness, and falls under the disability legislation instead
• Neurosis retains insight and psychosis does not, which is why the distinction carries all the forensic weight
• Get an informant history separately; a person without insight cannot give the account on which the diagnosis depends
• Record insight verbatim; it is the faculty on which responsibility, capacity and admission all turn
• Judge a belief against the community, not against your own; possession and witchcraft beliefs may be culturally normal and are not delusions
• Visual hallucination means look for a physical cause, and auditory hallucination usually does not
• Insight is what separates neurosis from psychosis, and it is assessed by asking whether the person believes they are ill
• Observe over days rather than deciding at one interview; both genuine illness and feigning declare themselves over time
• Give the opinion as a board in medicolegal cases, with the mental state examination set out in full
• Delusions of control and thought broadcasting are characteristic of schizophrenia and are worth eliciting specifically
• Lilliputian hallucinations of small animals point strongly to an organic withdrawal state rather than a functional psychosis
• Test cognition in every case — orientation, attention and memory — since it is what separates organic from functional illness
• Nihilistic and guilt delusions accompany severe depression, and carry a high risk of suicide and of extended suicide