Siddique Ali, 40, was freed by the Madras High Court following a plea by his 32-year-old wife so the couple can undergo fertility treatment.
The court order, made last week but only revealed on Thursday, is a rare judgment in India recognising prisoners' conjugal rights.
The judges said Ali was released under "extraordinary" circumstances for the "purpose of procreation".
They rejected a prosecution contention that the law does not provide for a prisoner to be freed to start a family.
The court order said the wife was "a suffering person" and "her legitimate expectation to have a child cannot be declined."
"Being human beings, prisoners also would like to share their problems with their life partner as well as the society. Just because they are termed as prisoner, their right to dignity can't be deprived," the 11-page judgement said.
The justices ordered Ali to return to prison on February 3 but said they would consider additional leave if required.
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Ali was convicted two years ago. Details of the murder were not immediately given.
The couple's lawyer said Ali and his wife are consulting fertility specialists.
"The doctors are conducting tests and we are hopeful their wish is fulfilled," the lawyer told AFP on condition of anonymity.
The judgement ordered the government to consider allowing conjugal visits for other prisoners.
An Indian court in 2015 ruled conjugal visits and artificial insemination are a fundamental right and said special facilities should be built for married inmates.
But such visits are rare in the notoriously overcrowded prisons.
Nearly 420,000 inmates were lodged in 1,400 Indian jails with a capacity of 366,000 prisoners, according to the last official figures from 2015.
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