Conviction for Offenses: Article 20 (Self-incrimination)

Article 20 protects accused persons (both citizens and foreigners) from arbitrary prosecution and retroactively applied criminal penalties.

1. Article 20(1) - Protection Against Ex-Post Facto Laws

The State cannot:

Convict a person for an act that was not an offense at the time it was committed.
Subject a person to a penalty greater than what was prescribed by law at the time the offense was committed.

Note: This protection applies only to criminal statutes, not to tax laws or civil liabilities.

2. Article 20(2) - Protection Against Double Jeopardy

Article 20(2) reads: "No person shall be prosecuted and punished for the same offence more than once."

Derived from the common law maxim Nemo debet bis vexari.
Requires both prosecution AND punishment before a court of law. Departmental disciplinary actions or police inquiries do not trigger double jeopardy (Maqbool Hussain v. State of Bombay).

3. Article 20(3) - Protection Against Self-Incrimination

Article 20(3) reads: "No person accused of any offence shall be compelled to be a witness against himself."

📜 Forensic Jurisprudence Milestone: Selvi v. State of Karnataka (2010)

The Supreme Court held that the involuntary administration of narco-analysis, polygraph tests, or brain mapping violates the protection against self-incrimination under Article 20(3) and the right to privacy under Article 21. Forcing these tests on an accused amounts to testimonial compulsion and is unconstitutional.