The Supreme Court will announce on Wednesday its verdict on biometric ID programme or Aadhaar.
A five-judge bench headed by CJI Dipak Misra has been hearing the Aadhaar case over the last four months. The bench will decide if the government can use it as a mandatory identification.
Some petitioners in the top court had termed the linking of the Unique Identification Authority of India (UIDAI) number with bank accounts and mobile numbers as "illegal and unconstitutional" and violated privacy rights.
The hearing of the Aadhaar case was one of the longest in the Supreme Court, second only to the landmark Kesavananda Bharati case.
Although Aadhaar was introduced during the time of the Congress-led UPA government, the Aadhaar (Targeted Delivery of Financial and other Subsidies, benefits and services) Act was passed in the Lok Sabha in March 2016, under the BJP government, as a money bill.
Although the first petition challenging the Aadhaar was filed in 2012, several new petitions were filed in subsequent years in the Supreme Court challenging different aspects of the Aadhaar project. The hearing in the case concluded in May 2018.