Justice Iyer, who turned 100 on November 15, breathed his last in Kochi following multiple organ failure.
He was admitted to the hospital on November 24. He died at 3.30 pm, the hospital managing director P V Antony and cardiologist Dr Manu R Varma, who treated him, said.
"The death was due to cerebral vascular accident or stroke, worsening cardiac and renal failure and pneumonia," Dr Varma said.
Justice Iyer, born in a conservative Tamil Brahmin family in Palakad in Kerala, was attracted to Communism and served as a minister in the first democratically-elected Communist government in the world under E M S Namboodiripad in the state.
During his tenure as law minister, land reforms were introduced in the 1950s. As a Supreme Court judge for seven years in the 1970s, he provided ordinary people easy access to the law by relaxing the rule of locus standi.
He defined bail jurisprudence in favour of undertrials when he laid down that 'Bail, not jail is the rule' and was averse to preventive detentions as a general rule.
In 1975, he stayed the Allahabad high court judgment that unseated then prime minister Indira Gandhi as an MP from Rae Bareli.
He praised Narendra Modi after he was named the Bharatiya Janata Party's prime ministerial candidate last year. Earlier, he had been critical of Modi on the 2002 riots.
'My association with Justice Krishna Iyer was special,' the prime minister said, mourning the judge's death. 'My mind goes back to our conversations and the insightful letters he would write to me.'
He is survived by two sons. His wife had predeceased him. At the time of his death, his son Parameshwaran and daughter-in-law were by his side.
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