Forensic Medicine and Toxicology
Forensic Psychiatry
Forensic psychiatry for MBBS: delusions and hallucinations, McNaughten rules, true versus feigned insanity, delirium tremens and the Mental Healthcare Act 2017, mapped to NMC codes FM5.1 to FM5.6.
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Forensic Psychiatry
Forensic psychiatry for MBBS: delusions and hallucinations, McNaughten rules, true versus feigned insanity, delirium tremens and the Mental Healthcare Act 2017, mapped to NMC codes FM5.1 to FM5.6.
Forensic psychiatry sits at the meeting point of mental illness and the law. This chapter covers the key psychopathology terms, the assessment of civil and criminal responsibility including the McNaughten rules, the distinction between true and feigned insanity, and the framework of the Mental Healthcare Act 2017.
High-yield: Forensic Psychiatry
- A delusion is a fixed false belief not shared by the person's culture and unshakeable by reason; a hallucination is a perception without an external stimulus.
- An illusion is a misinterpretation of a real external stimulus and can occur in healthy people.
- A lucid interval is a period of apparent sanity between episodes of mental illness, important when judging responsibility for an act.
- The McNaughten rules test criminal responsibility: the accused is not liable if, due to a defect of reason from disease of the mind, he did not know the nature of the act or that it was wrong.
- True insanity is a genuine disorder, while feigned or malingered insanity is faked, usually to escape punishment, and is exposed by inconsistency and lack of true symptom clusters.
- Testamentary capacity requires that a person understand the nature of a will, the extent of their property and the claims of those they may benefit.
- Delirium tremens is an alcohol withdrawal emergency with tremor, agitation, disorientation and vivid visual hallucinations, and can be fatal.
- The Mental Healthcare Act 2017 decriminalised the attempt to commit suicide, presuming severe stress in such persons.
- The Mental Healthcare Act 2017 gives every person the right to make an advance directive and to nominate a representative for their mental health care.
- Admission under the Mental Healthcare Act may be independent (voluntary) or supported, with review board oversight for prolonged supported admission.
- Post-traumatic stress disorder follows exposure to a severe threat and features re-experiencing, avoidance and hyperarousal.
- A person of unsound mind cannot give valid consent to treatment or to sexual intercourse.
- Somnambulism and automatism describe acts performed without conscious awareness and may bear on legal responsibility.
- Irresistible impulse and diminished responsibility are recognised in some jurisdictions but are applied cautiously by Indian courts.
- The doctor's role is to assess and document the mental state objectively, not to pronounce the final verdict on responsibility, which rests with the court.
Core psychopathology terms
- **Delusion:** Fixed false belief, out of keeping with culture, not corrected by reason.
- **Hallucination:** Perception without any external stimulus, most often auditory in psychosis.
- **Illusion:** Misinterpretation of a real external stimulus; can occur in health.
- **Lucid interval:** Spell of apparent sanity between episodes; relevant to responsibility and to head injury.
NMC competencies in this chapter
- **FM5.1:** Common mental illnesses and PTSD in forensic settings
- **FM5.2:** Delusions, hallucinations, illusions, lucid interval and obsessions
- **FM5.3:** Civil and criminal responsibility in mental illness
- **FM5.4:** True insanity and feigned insanity
- **FM5.5:** Delirium tremens as a forensic emergency
- **FM5.6:** The Mental Healthcare Act 2017: admission, care and discharge
Frequently Asked Questions
What are the McNaughten rules?
They test criminal responsibility. A person is not liable if, because of a defect of reason from disease of the mind, they did not know the nature of the act or that it was wrong.
How is feigned insanity detected?
By inconsistency over time, symptoms that do not cluster as in a real disorder, over-acting when watched, and normal behaviour when the person believes they are unobserved.
What did the Mental Healthcare Act 2017 change about suicide?
It presumes that a person attempting suicide is under severe stress and shall not be tried or punished, effectively decriminalising the attempt and directing care instead.
Why is delirium tremens a forensic emergency?
It is a severe alcohol withdrawal state with agitation, disorientation and vivid hallucinations that can be fatal, and acts done in it raise questions of responsibility and custody care.
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