Article 20 (1) of the Constitution is as follows:

“No person shall be convicted of any offence except for violation of a 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.”

This Article, in its broad import has been enacted to prohibit conviction and sentences under ‘ex post facto’ laws. The principle underlying such prohibition has been very elaborately discussed and pointed out in the very learned judgment of Justice Willes in the well known case of ‘Phillips vs. Eyre’, (1870) 6 QB 1 at pp. 23 and 25 (D), and also by the Supreme Court of U. S. A. in – ‘Calder vs. Bull’ (1798) 3 Dallas 386: 1 Law Ed 648 at p. 649 (E). In the English case it is explained that ‘ex post facto’ laws are laws which voided and punished what had been lawful when done. There can be no doubt as to the paramount importance of the principle that such ‘ex post facto’ laws, which retrospectively create offences and punish them are bad as being highly inequitable and unjust. In the English system of jurisprudence repugnance of such laws to universal notions of fairness and justice is treated as a ground ‘not’ for invalidating the law itself but as compelling a beneficent construction thereof where the language of the statute by any means permits it. In the American system, however, such ‘ex post facto’ laws are themselves rendered invalid by virtue of Art. 1 Ss. 9 and 10 of its Constitution. It is contended by the learned Attorney-General that Art. 20 of the Constitution was meant to bring about nothing more than the invalidity of such ‘ex post facto’ laws in the post-Constitution period but that the validity of the pre-Constitution laws in this behalf was not intended to be affected in any way.

The case in – ‘Keshavan Madhavan Menon vs. State of Bombay’, AIR 1951 SC 128 (F), has been relied on to show that the fundamental rights guaranteed under the Constitution have no retrospective operation, and that the invalidity of laws brought about by Art. 13 (1) of the Constitution relates only to the future operation of the pre-Constitution laws which are in violation of the fundamental rights. On this footing it was argued that even on the assumption of the convictions in this case being in respect of new offences created by Ordinance No. 48 of 1949 after the commission of the offences charged, the fundamental right guaranteed under Art. 20 is not attracted thereto so as to invalidate such convictions. This contention, however, cannot be upheld. On a careful consideration of the respective Articles, one is struck by the marked difference in language used in the Indian and American Constitutions. Sections 9 (3) and 10 of Art. 1 of the American Constitution merely say that “No ‘ex post facto’ law shall be ‘passed’ . . . . .. . . “ and “No State shall “pass ex post facto’ law . . … . . . . .. . . ..” But in Art. 20 of the Indian Constitution the language used is in much wider terms, and what is prohibited is the conviction of a person or his subjection to a penalty under ‘ex post facto’ laws. The prohibition under the Article is not confined to the passing or the validity of the law, but extends to the conviction or the sentence and is based on its character as an ‘ex post facto’ law. The fullest effect must therefore be given to the actual words used in the Article. Nor does such a construction of Art 20 result in giving retrospective operation to the fundamental rights thereby recognised. All that it amounts to is that the future operation of the fundamental right declared in Art. 20 may also in certain cases result from acts and situations which had their commencement in the Pre-Constitution period

In – ‘The Queen vs. St. Mary Whitechapel’, (1848) 116 ER 811 at p. 814 (G), Lord Denman C. J. pointed out that a statute which in its direct operation is prospective cannot properly be called a retrospective statute because ‘a part’ of the requisite for its action is drawn from a time antecedent to its passing. The general principle, therefore, that the fundamental rights have no retrospective operation is not in any way affected by giving the fullest effect to the wording of Art. 20. This Article must accordingly be taken to prohibit all convictions or subjections to penalty after the Constitution in respect of ‘ex post facto’ laws whether the same was a post Constitution law or pre-Constitution law. That such is the intendment of the wording used in Art. 20 (1) is confirmed by the similar wording used in Arts. 20 (2) and 20 (3). Under Art. 20 (2)1 for instance, it cannot be reasonably urged that the prohibition of double jeopardy applies only when ‘both’ the occasions therefor arise after the Constitution. Similarly, under Art. 20 (3) it cannot be suggested that a person accused before the Constitution can be compelled to be a witness against himself, if after the Constitution the case is pending.

In this context it is necessary to notice that what is prohibited under Art. 20 is only conviction or sentence under an ‘ex post facto’ law and not the trial thereof. Such trial under a procedure different from what obtained at the time of the commission of the offence or by a Court different from that which had competence at the time cannot ‘ipso facto’ be held to be unconstitutional. A person accused of the commission of an offence has no fundamental right to trial by a particular 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 right may be involved.