The term “Public Interest Litigation” was originally borrowed from the American Jurisprudence, where they provided legal representation and guidance to unpresented groups like the racial minorities, unorganized groups, poor etc. Public Interest Litigation is filed regarding any issue where the public at large are affected such as Construction hazards, Pollution, Terrorism etc. It is a sense of power bestowed upon the public which is authorised by the courts through judicial activism. There is no definite statute or act which defines Public Interest Litigation. The key thing to remember while filing a PIL is that the petitioner should not file a PIL for any frivolous matter, it should be filed for a public interest at large. Public Interest Litigation has played a pivotal role in the civil justice system. It protects those who are victims of oppression, are deined their fundamental rights, legal right etc. It acts as a support system for those who are not in the position and are vulnerable to approach the court due to lack of resources, for the redressal of their grievances. It enables the society to not only participate in the government decision making but also spread awareness about human rights.
The term “Locus Standi” means having the legal capacity to challenge an act or decision made by the court of law. There must be a legal issue or violation of rights then only one can approach the court. Locus Standi refers to the right of an aggrieved party to approach the court. However there lies a difference between traditional adjudication system and Public interest Litigation . Before 1980s, in India, it was only the aggrieved party that could seek justice in the Court of law and a person who was not affected personally could not approach the Court as a representative of the aggrieved party. Thus, the locus standi was vested only in the aggrieved affected party to file a case in the Courts. Due to this there was a gap in the fundamental rights promised by the Constitution on one hand and the laws on the other and it was the rights of the poor, illiterate and underprivileged that remained neglected and abandoned by the entirely legal system. Therefore, in order to acquire a locus standi a personal legal right of an individual must be threatened or violated. However the scenario changed in the Eighties when the Supreme Court introduced the ideology of Public Interest Litigation in India.
Some Cases which can be covered under Public Interest Litigation are:
Exploitation and non payment of labours
Atrocities towards women and children
Matters concerning about the environment and ecological imbalance
Complaints for misuse of power and harassment by the police
Origin of The Public Interest Litigation
The concept of Public Interest Litigation was originally adopted from the United States Of America during the mid 1960, applied by Louis Brandeis who uphold the interest of the general public. The Origin of Public Interest Litigation can be traced by to the legal aid movement which took place in the United States Of America. In 1876 an organized Legal Aid Movement was established for the poor people, the credit goes to Reginald Heber Smith for taking the first step towards development of Legal Aid. The Second stage was when the organized form of Legal Aid included motivated law firms devoted solely towards legal aid programmes. In U.S.A. it is called the ‘Public Interest Law’ whereas in the Indian Subcontinent it is known as ‘Public Interest Litigation’
The Constitution Of India Regarding Public Interest Litigation
Public Interest Litigation is based upon Article 39 A. Under the Constitution of India, Article 39A, it makes sure that the state secures and provides justice without any discrimination on the basis of caste, religion, creed etc 
The Writ Jurisdiction of the Supreme Court can be invoked under Article 32 and in the High Court under Article 226 of the Indian Constitution when there has been a violation of the Fundamental Rights of an individual or a group. The Fundamental Rights guaranteed under part III of the Constitution, are enforceable and justiciable and any law which is inconsistent or nullifies the Fundamental Rights is void. The main difference between Article 32 and 226 is that the former can be invoked for the fundamental rights only whereas the later can be invoked for the fundamental rights as well as for any other purpose.
Evolution of Public Interest Litigation in India
In Fertilizer Corp. Kamgar Union v Union of India the Court reiterated that with an expansion of bureaucratic power, there was an increased chance of misuse of legal standing, and thus greater flexibility was the need of the hour. The concept of locus standi was widened to deal with the ever-expanding scope of socio-economic justice.
Public Interest Litigation in India was founded by Justice Krishna Lyser in Mumbai Kamagar Sabha vs Abdul Thai In 1976. The case dealt with the payment of bonus to the workmen of an industry. It was initiated in Railways vs Union of India in which an workers were permitted to issue a writ petition for redress of common grievances.
First case of Public Interest Litigation in India was in 1979, it was based on the conditions of the prisoners and under trial prisoners. In Hussainara Khatoon vs State of Bihar, the PIL filed was regarding the situation of thousands of under trial prisoners in numerous jails in Bihar. The proceedings impacted on the release of more than 40,000 under trial prisoners. . The Supreme Court held that in matters which are in the larger interest of the public right to speedy justice is a Fundamental Right, which comes within the scope of ‘life’ and ‘personal liberty’ guaranteed under Article 21. The same set pattern was adopted in subsequent cases
In the case of S.P Gupta vs Union of India, heard by Justice P.N Bhagawati, it was held that any member of the society seeking redressal against violation of legal rights, who cannot approach the court, can invoke the Writ Jurisdiction of the Supreme Court or High Court. Through this Judgement PIL became a profound weapon for enforcement of public duties. As a result any citizen of can now approach the court for seeking legal remedies where the interests of general public is at stake. Justice Bhagwati even treated ordinary letters from public-minded individuals as writ petitions.
In the case of Anil Yadav vs State of Bihar held in 1981, exposed the police brutality. The police at Bihar, Bhagalpur jail, mercilessly burnt the eyes of about thirty three victims by throwing acid in their eyes. The Supreme Court condemned the police rigorously and ordered the Bihar government to bring the blinded people for medical treatment to Delhi, at the states expense. Free legal aid as a fundamental right as an aspect of right to life and personal liberty was declared by the Supreme Court
In People’s Union for Democratic Rights v Union of India, an organization working towards securing the democratic rights of the people complaining of breaches of labour laws who were workers engaged in the construction of Asiad projects was brought before the Supreme Court under Article 32. Justice P N Bhagwati in the instant case explained that a PIL is not brought before the Court only to enforce the rights of one individual against another which is what happens under the ordinary traditional litigation. Instead, it is filed to enforce the collective rights of a class of persons whose Fundamental Rights have been violated. 
Public Interest Litigation(PIL) has shown remarkable results which we never thought we could achieve three decades ago. Many people such as labourers, women prisoners, exploited and underprivileged children, beggars, etc have been given relief through judicial intervention . Public Interest Litigation serves as a ladder to the disadvantaged and underprivileged sections of the society,plays an important role in the civil justice. It also enables the society to spread awaraness about human rights, legal rights and participate in government decision making .
Significance of PIL
PIL plays a crucial role for maintaing rule of law and helps in social change
Purpose of PIL is to make justice accessible to the venerable sections of the society
Helps to implement the concept of judicial review
An important instrument to make human rights reach to those who have been denied rights.
It makes justice accessible to everyone, any citizen or organization can file petition on behalf of others who are not capable to do so
The Constitution Of India 1949, Article 39(a)
The Constitution Of India 1949, Article 32
The Constitution Of India 1949, Article 226
Fertilizer Corporation Kamgar vs Union Of India  AIR 344, 1981 SCR (2) 52
Mumbai Kamgar Sabha, Bombay vs M/S Abdulbhai Faizullabhai & Ors  AIR 1455, 1976 SCR (3) 591
National Federation Of Railway vs Union Of India And Ors  WP (civil) 507 of 1992
Hussainara Khatoon & Ors vs Home Secretary, State Of Bihar  AIR 1369, 1979 SCR (3) 532
S.P. Gupta vs President Of India And Ors  AIR 1982 SC 149, 1981 Supp (1) SCC 87, 1982 2 SCR 365
Anil Yadav & Ors vs State Of Bihar & Anr  AIR 1008, 1982 SCR (3) 533
Citizens For Democracy vs State Of Assam And Ors  WP (civil) 22 of 1995
People'S Union For Democratic vs Union Of India & Others  AIR 1473, 1983 SCR (1) 456