How does India Decide Insanity Pleas? A Review of High Court Judgments in the Past Decade.

Background: The Section 84 of the Indian Penal Code (IPC) describes how Indian courts have to deal with 'the act of an unsound person'. This study was undertaken with the objectives of estimating the success rate of insanity pleas in Indian High Courts and determining the factors associated with the outcome of such insanity pleas.

Materials and Methods: The data was collected from the websites of 23 High Courts of India using the keywords 'insanity' and 'mental illness', and the judgments delivered between 1.1.2007 and 31.08.17 were retrieved. Information regarding the nature of the crime, diagnosis provided by the psychiatrist as an expert witness, documents used to prove mental illness, and the judgment pronounced by the High Court were retrieved.

Results: A total of 102 cases were retrieved from 13 High Courts for which data was available. Out of the 102 cases examined, the High Court convicted the accused in 76 cases (74.50%), thereby rejecting the insanity defense. The High Court acquitted the accused under section 84 IPC in 18 cases (17.65%), thereby accepting the insanity plea raised by the accused. Chi-square tests of independence revealed that the verdict of the lower court, documentary evidence of mental illness prior to the crime, and the psychiatrist's opinion were associated with the success of insanity pleas.

Conclusion: Insanity pleas had a success rate of about 17% in Indian High Courts in the past decade. The factors associated with success of insanity pleas provide valuable guidance to several stakeholders who are dealing with mentally ill offenders.