• Objective: It provides protection against arbitrary and excessive punishment for an accused individual, regardless of whether they are a citizen, a foreigner, or a legal entity like a corporation. 
• Importance: Article 20 cannot be suspended even in times of emergency, making it a fundamental aspect of the liberties and freedoms guaranteed by the Indian constitution. 
• Applicability: The protections established by Article 20 are applicable to everyone, including both citizens and foreign nationals

No ex-post-facto law [Article 20(1)]

• No person shall be convicted of any offense unless it breaches a law that was in effect at the time the act was committed. 
• No person shall face a penalty greater than what is prescribed by the law in force at the time of the act’s commission. 
• Ex-post-facto law: An ex-post facto law refers to legislation that imposes penalties retroactively, meaning on actions that have already taken place, or that increases the penalties for those actions. In terms of criminal law, the introduction of such laws is prohibited by Article 20.  
• Scope of retrospective laws: The legislature has the authority to enact both prospective and retrospective laws. However, when it pertains to criminal matters, the legislature is barred from enacting retrospective legislation. In other words, retrospective liabilities or taxes can be established, but not criminal penalties. 
• Prohibition: This clause specifically prohibits conviction or sentencing under a retroactive criminal law, but it does not prevent the trial itself. 
• Preventive detention: The immunity provided by this clause is not applicable in cases of preventive detention or in circumstances where a person is required to provide security. 
• Nirbhaya case: Following the horrific gang-rape incident that occurred in Delhi, public opinion strongly supported harsher penalties for the six accused. However, because one of them was a minor, amending the juvenile age would not have an ex-post facto application, and thus would not impact the case. 

No double jeopardy [Article 20(2)]

• No person shall face prosecution and punishment for the same offense more than once. 
• The protection against double jeopardy applies solely in court proceedings or before a judicial tribunal. It does not extend to cases heard by departmental or administrative authorities, as those are not judicial in nature

However, the application of this provision does demand certain conditions to be fulfilled: 

• Tried before by the court: The accused or the person in question must have been tried by the court previously and it is concerned only with judicial prosecution and proceedings.
• Trial by a Competent court: The court trying the case must be competent, i.e. it should act under its competent jurisdiction.
• Conclusion of proceeding: The previous proceeding must have ended in either acquittal or conviction and if it ended merely after inquiry, such cases are not covered under this provision of ‘no double jeopardy’.
• In force: The previous conviction/acquittal must be in force and should not have been set aside by appeal or retrial. This is an essential condition because in absence of previous conviction, there will be no bar for the second prosecution and the second trial may happen.
• Tried for same offence: In the subsequent trial, he/she must be tried for the same offence and on the same facts for any other offence, which is having a different charge under the CrPC.

No self-incrimination [Article 20(3)]

• No person charged with a crime shall be forced to testify against their own interests. 
• This protection applies exclusively to criminal cases and does not pertain to civil cases or other non-criminal proceedings.

Relevant Judgement

State of Bombay Vs Kathi Kalu Oghad 1961

In this ruling, the Supreme Court determined that the right against self-incrimination covers both oral and documentary evidence. Nonetheless, this right does not extend to the mandatory production of physical items, providing thumb impressions, specimen signatures, blood samples, or the exhibition of the body.