Which movement in India led to the filing of Public Interest Litigation and the Judiciary had to give decision over PIL?

Hussainara Khatoon vs State of Bihar case was one such movement in India led to the filing of Public Interest Litigation and the Judiciary had to give decision over PIL. As the case was filed by the prisoner named Hussainara Khatoon. So it came to be known as Hussainara Khatoon vs State of Bihar case. The case was filed because in prison some of the prisoners were held more than their punishable imprisonment as they were waiting for their trial procedure. As a result, one of the prisoners filed PIL and the Judiciary had to give decision over PIL. The result was then taken to provide free and fair legal services to the needy people, Article 39A stated to provide free and fair legal services to the needy people otherwise the individual will not be able to secure Justice, government of India and state government was informed to introduce proper legal service programme and the state should provide speedy trial to the victim with lack of financial and administrative help.

NOTE- Public Interest Litigation (PIL) is introduced by the Person or Public to seek a solution in the interest of a person or group (oppressed class).