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The rights imbibed in part III of the Constitution of India forms the most basic and fundamental rights which are provided to the citizen, some are given to non-citizens also, of the country and puts obligations on the state. The concept of fundamental rights borrowed from the United States of America and divided into the justifiable and non-justifiable part which was later developed into Part IV of the Constitution. Part III contains Articles 12 to 35. Article 20 is related to the protection of people related to a conviction for offences which include the right against self-incrimination, right against double jeopardy and ex post facto laws. Article 21 is related to the right to life. Both these rights are available to citizens and non-citizens except enemy aliens. Both the rights are non-derogable rights that cannot be removed in an emergency. Along with the constitutional mandate, these rights have also judicial development and mandate. Judiciary keeps defining these rights and their applicability. The judiciary gave landmark judgements that change nature and expand the scope of these rights.
ARTICLE 20: LEGAL DEVELOPMENT
Article 20 of the Constitution says
“Protection in respect of conviction for offences
(1) No person shall be convicted of any offence except for violation of the law in force at the time of the commission of the act charged as an offence, nor be subjected to a penalty greater than that which might have been inflicted under the law in force at the time of the commission of the offence
(2) No person shall be prosecuted and punished for the same offence more than once
(3) No person accused of any offence shall be compelled to be a witness against himself.”
There are many judgements that explain the meaning of these clauses.
“1) No person shall be convicted of any offence except for violation of the law in force at the time of the commission of the act charged as an offence, nor be subjected to a penalty greater than that which might have been inflicted under the law in force at the time of the commission of the offence.”
Clause 1 of article 20 is related to the ex-post facto laws which mean laws cannot be applied retrospectively with exceptions. Ex. A crime of murder was committed in 1816 but at that time there was no such law that punishes the murder. During the prosecution, the law was made which criminalise murder and gives 1 year of imprisonment, but according to clause (1) of Article 20, punishment cannot be given on the basis of this new law.
The latter part of the clause also denies an increase in punishment. Like in the above example, even 1 day extra in punishment cannot be awarded.
This clause can better understand by dividing it into four parts
1. “NO PERSON SHALL BE CONVICTED”- Take note of the word ‘Convicted’. This clause prohibits the conviction but not the trial. The trial of an offence can be done in the new prescribed way. “A person accused of the commission of an offence has no fundamental right to trial by a court or by a particular procedure except in so far as any constitutional objection by way of discrimination or the violation of any other fundamental rights may be involved.” 
2. “ANY OFFENCE”- Take note of the word ‘offence’. As such there is no definition of the word ‘offence’ in the constitution. The Supreme Court clarified this in Jawala Ram v. the State of Pepsu “the word “Offence in several clauses of Art. 20 must be understood to convey the meaning given to it S.3 (38) of the General Clauses Act. That section defines an “offence” to mean an act or omission made punishable by any law for the time being in force.”
So, it is clear that this article is related to an act or omissions which are punishable by any at that time. The increase in the levy imposed on any article or any such law is not covered under this article. Civil liabilities and revenue laws are not covered under article 20.
3. “LAW IN FORCE”- This whole phrase is important. “The phrase “law in force” as used in Art. 20 must be understood in its natural sense as being the law in fact in existence and in operation at the time of the commission of the offence as distinct from the law “deemed” to have become operative by virtue of the power of Legislature to pass retrospective laws.” Here, it becomes important to know Section 24 of the General Clauses Act which says that any repealed and re-enacted then the rules of the repealed act will be continued to be deemed to be law unless they are inconsistent with the re-enacted law. Under Art. 20, this will be considered as ‘law in force’. 
Fundamental rights also do not have any retrospective operation but applying the Art. 20 in its fullest meaning does not affect this provision. “Article 20(1) must accordingly be taken to prohibit all convictions or objections to a penalty after the Constitution in respect of ‘ex post facto’ laws whether the same was a post-Constitution law or pre-Constitution law.” 
4. “PENALTY GREATER”- It is the other part of this clause. It puts the limit to apply the increased penalty on the said crime or offence which was committed before the enactment of that law. But it does not limit the punishment. As the Supreme Court in K. Satwant Singh v. State of Punjab  observed that “[A] law which provides for a minimum sentence of fine on conviction cannot be read as one which imposes greater penalty than that which might have been inflicted under the law at the time of the commission of that offence.”
“(2) No person shall be prosecuted and punished for the same offence more than once.”
As the fundamental rights are taken from the USA but the Art.20 (2) has a narrower concept than that of the USA. This article stops the harassment of a person by prosecuting and punishing again and again. A person who was prosecuted for an offence but acquitted by the court, if he is again prosecuted for the same offence does not violate the Art. 20 (2).  An appeal against the acquittal of the person is not the second prosecution but the continuance of the first prosecution. An enquiry by the enquiry commission under Public Service Enquiry Act, 1960 and after it, the suspension of a from the service do not form the prosecution. A person can be prosecuted for two different offences, to invoke Art. 20 (2), offences needed to be the same and the similarity to be judges from the ingredients of the offence not on the fact of the offence. 
“3) No person accused of any offence shall be compelled to be a witness against himself.”
1. “TO BE A WITNESS”- To be a witness means to give a personal testimony either oral or written. Its authority also needed to check whether that is excluded by the hearsay. Fingerprints, handwriting do not violate the Art. 20 (3) as they are not the personal testimony but they are unchangeable except in some cases. This article calls that an accused shall not be compelled “to be a witness against himself” not “to be a witness.” 
2. “COMPULSION”- Compulsion here is a physical objective act and not the state of mind of the person making the statements, except where the mind has been so conditioned by some extraneous process as to render the making of the statement involuntary and, therefore, extorted. Hence, the mere asking by a police officer investigating a crime against a certain individual to do a certain thing is not compulsion with the meaning of Art. 20 (3).
The Court in NandiniSatpathy v. P.L. Dani observed, “Narco Analysis without the informed consent of the accused would tantamount to ‘compelled self-incrimination, even if the result is not admitted as evidence in a Court of law”. The Court in the above case made the observation that - “relevant replies which furnish a real and clear link in the chain of evidence indeed to bind down the accused with the crime become incriminatory and offend Article 20(3) if elicited by pressure from the mouth of the accused.” Thus, Nacro Analysis without consent is a blatant violation of the Art. 20 (3). But Nacro Analysis is an investigative tool that has legal sanction in the existing provisions of the CrP.C. Nacro Analysis can be exempted from the right to privacy as it is not an absolute right.
Article 21 of the Constitution says
“Protection of life and personal liberty- No person shall be deprived of his life or personal liberty except according to the procedure established by law.”
This article provides the basic right to life against the state. This article remained in the narrower concept till the starting years of the constitution (A.K. Gopalan v. the State of Madras). Later on, its scope was broadened. This expands the scope of fundamental rights. The new rights began to develop under the ambit of this article. The right to a safe environment developed in the 1970s under this article as an environment is one of the basic needs of men. In Maneka Gandhi v. Union of India, the Court held that Article 21 is not water-tight compartments and in Unni Krishnan v. the State of A.P,the court itself provided the list of rights which come under this article.
“1. The right to go abroad.
2. The right to privacy.
3. The right to shelter.
4. The right to social justice and economic empowerment.
5. The right against solitary confinement.
6. The right against handcuffing.
7. The right against delayed execution.
8. The right against custodial death.
9. The right against public hanging.
10. Doctor’s assistance
11. Protection of cultural heritage.
12. Right of every child to full development.
13. Right to pollution-free water and air.”
In 2018, the Court in the Common Cause case allowed passive Euthanasia under strict guidelines. D.Y. Chandrachud observed that “Life and death are inseparable. Every moment our bodies undergo change… life is not disconnected from death. Dying is a part of the process of living.” K.S. Puttaswamy judgement on Article 21 was also a landmark judgment.
1. Shiv Bahadur Singh Rao v. The State of U.P, AIR 1953 SC 394.
2. AIR 1962 SC 1246.
3. Shiv Bahadur Singh Rao v. The State of U.P, AIR 1953 SC 394.
4. Chief Inspector of Mines v. Lala Karam Chand Thapar, AIR 1961 SC 838.
5. The Queen v. St. Mary Whitechappel, (1848), 16 ER at 814.
6. AIR 1960 SC 266.
7. Leo Roy v. Superintendent District Jail, AIR 1958 SC119.
8. Smt. Kalawati v. state of H.P., AIR 1953 SC 131 at p.152.
9. Venkataraman v. Union of India, AIR 1954 SC 375.
10. The State of Bombay v. S.L. Apte and Anr., AIR 1961 SC 578.
11. State of Bombay v. KathiKaluOghad, AIR 1961 SC 1808.
13. 1978 AIR 1025.
14. 1950 AIR 27.
15. 1978 AIR 597.
16. 1993 AIR 2178.