A highly technical issue is resolved in affirmative, by the 5-judge Constitutional Bench by interpreting a term, ‘TERM‘.

Whether persons sentenced to imprisonment for life entitled to set-off their under trial period of detention against their sentence?

The Bench said,

Life is uncertain. In more ways than one. Who knows what good may come tomorrow and how many good tomorrows there are still to go ? But , philosophical digressions apart , especially optimistic , the fact that the term of life is of an uncertain duration does not justify the conclusion that the sentence of imprisonment for life is not for a term. The relevant question and , the only one , to ask under section 428 is: Has this person been sentenced to imprisonment for a term ? For the sake of convenience , the question may be split into two parts. One, has this person been sentenced to imprisonment ? And, two, is the imprisonment to which he has been sentenced an imprisonment for a term ? There can possibly be no dispute that a person sentenced to life imprisonment is sentenced to imprisonment. Then , what is the term to which he is sentenced ? The obvious answer to that question is that term to which he has been sentenced is the term of his life. Therefore , a person who is sentenced to life imprisonment is sentenced to imprisonment for term.

In conclusion,

We have considered with great care the reasoning upon which the decision in Kartar Singh proceeds. With respect, we are unable to agree with the decision. We have already discussed why ’imprisonment for life is imprisonment for a term , within the meaning of section 428. We would like to
add that we find it difficult to agree that the expressions ’imprisonment for life’ and imprisonment for a term’ are used either in the Penal Code or in the Criminal Procedure Code in contra-distinction with each other. Sections 304 , 305 , 307 and 391 of the penal Code undoubtedly provide that persons quilty of the respective offences shall be punished with imprisonment for life or with imprisonment for a term not exceeding a certain number of years. But , that is the only manner in which the Legislature could have expressed its intention that persons who are guilty of those offences shall be punished with either of the sentences mentioned in the respective sections. The circumstance on which the learned judges have placed reliance in Kartar Singh , do not afford any evidence , intrinsic or otherwise’ of the use of the two expressions in contra-distinction with each other. Two or more expressions are often used in the same section in order to exhaust the alternatives which are available to the Legislature. That does not mean that there is , necessarily , an antithesis between those expressions.
The reasoning in Kartar Singh that an order of remission does not interfere with the sentence recorded by the court but merely affects the execution of the sentence, stands answered by the interpretation which we have put upon the language of section 428 that persons sentenced to imprisonment for life are sentenced to imprisonment for a term. It is not because of remission that a sentence of life imprisonment becomes an imprisonment for a term.
We have also already answered the last of the reasons given in Kartar Singh that the question is not whether the beneficent provision contained in section 428 should be extended to life convicts on equitable considerations. We enter a most respectful caveat. Equity sustains law and the twain must meet. They cannot run in parallel streams. Equitable considerations must have an important place in the construction of beneficent provisions, particularly in the field of criminal law. To exclude such considerations is to denude law’s benevolence Or its true and lasting content. Lastly , the view expressed by the Joint Committee in its Report does not yield to the inference that the “mischief sought to be remedied has no relevance where gravity of offence requires the imposition of imprisonment for life”. As we have indicated earlier , graver the crime , longer the sentence and , longer the
sentence , greater the need for set-offs and remissions. Punishments are no longer retributory. They are reformative.
The order passed by this Court in Sukhlal Hansda related to the cases of 24 prisoners who were sentenced to life imprisonment. Most of those prisoners had undergone imprisonment for a period which , after taking account the remissions earned by them , exceeded fourteen years. It was
held by this Court that , for the purpose of considering whether the cases of those prisoners should be examined for premature release under the relevant provisions of the West Bengal Jail Manual , there was no reason why the period of imprisonment undergone by them as undertrial prisoners
should not be taken into account. The Court directed that the cases of the prisoners should be considered by the State Government , both for the purpose of setting off the period of detention undergone by them as undertrial prisoners and for taking into account the remissions earned by them. The order passed by the Court does not discuss the point which arises before us though , the observations made therein are consistent more with the view which we have taken than with the view taken in Kartar Singh.

Citations : [1985 SCC CRI 280], [1985 SCALE 1 719], [1985 AIR SC 1050], [1985 SCC 2 580], [1985 CRIMES SC 1 832], [1985 SCR 3 743], [1985 CRILJ 1179], [1985 AWC 11 510], [1985 BOMLR 85 400], [1985 ACR 340]

Other Sources :

https://indiankanoon.org/doc/733492/

https://www.casemine.com/judgement/in/5609ac19e4b014971140e060