[3] In 1948, when he protested the evil of torture by police for interrogation, he was imprisoned for a month on a fabricated charge of giving legal assistance to communists.

[11] He was a Minister between 1957 and 1959 in the government led by E. M. S. Namboodiripad, holding the portfolios for Home, Law, Prison, Electricity, Irrigation, Social Welfare and Inland Water.

[11] He initiated legal-aid to the poor, jail reforms incorporating the rights of prisoners, and set up more courts and rescue homes for women and children.

[10] Iyer was a member of the Law Commission of India from 1971 to 1973 where he drafted a comprehensive report, which would lead to the legal-aid movement in the country.

[3] Iyer made notable contributions in the field of constitutional law, focusing on social, political, and civil rights.

[10] Along with Justice P. N. Bhagwati, he introduced the concept of PILs (Public Interest Litigations) or "people's involvement" in the country's courts with a series of cases.

[12] This revolutionary tool, initially used by public-spirited citizens to file PILs on behalf of sections of society unable to on their own, continues to bring in unheard changes in the day-to-day lives of the people even now, decades later.

[14] In June 1975, the Allahabad High Court had ruled that Prime Minister Indira Gandhi's election to Parliament was unlawful, and barred her from it for another six years.

[20] In Muthamma's case, Iyer called for breaking the 'glass ceiling' with gender parity in traditional practices in public employment.

[23][10] In Ediga Anamma v State of Andhra Pradesh, he established the jurisprudence governing the commuting of death sentences to imprisonment for life, identifying mitigating factors that could be applied in such cases.

[10] He retired as a judge on 14 November 1980 but, continued to advocate the cause of justice, on every forum and through his writings, participating in street protests,[24] and his house would always remain open, bustling with all who sought his help[25] or advice.

As a public intellectual Iyer held several positions in the people's organizations, arts societies, sports councils, and cultural groupings.

Upon his demise, his private library was donated to the National University of Advanced Legal Studies, where the Justice Krishna Iyer Collection still resides.