A change frequently encounters opposition from analytical minds prior to being embraced. This paper discusses the complex biological, psychological and social causes of criminal tendencies and their neurological triggers. The endocrine system, notably cortisol, changes behaviour and cognitive functions, which might lead to criminal tendencies when exposed to prolonged stress and adverse socio-economic conditions. The paper discusses the legal framework under Section 84 of the Indian Penal Code, presently Section 22 of the Bharatiya Nyaya Sanhita, 2023 (BNS). The authors contend that Indian criminal law failed to decolonize when the BNS preserved the same idea of “unsoundness of mind” without much alteration. The study examines issues in defining “unsoundness of mind” and how the accused bears the burden of proof. The authors also support diminished responsibility as a legal defence in accordance with international precedents and emphasize that legislative adjustments must embrace scientific developments. The article emphasizes rehabilitation and community-based therapy over punishment, citing the Mental Health Care Act, 2017, for neurologically impaired offenders. It suggests cognitive–behavioural therapy, education and vocational training for young offenders. The findings of this research suggest that a neuroscientific-informed legal system can improve justice, public safety and offender reintegration by prioritizing rehabilitation over punishment.