Vinay Sharma, one of the four death-row convicts in the 2012 Delhi gangrape and murder case, on Friday approached the Delhi High Court claiming “constitutional irregularities” and procedural lapses in the rejection of his mercy petition by President Ram Nath Kovind last month, PTI reported.

In his petition, Sharma claimed that the recommendation sent to the President to reject his mercy plea did not have Delhi Home Minister Satyendra Jain’s signature. Sharma’s lawyer AP Singh filed the petition on his behalf.

Sharma’s mercy petition had been rejected by Kovind in February.

On January 14, the Supreme Court had rejected Sharma’s curative petition along with that of Mukesh Singh, another convict in the case. In Sharma’s curative plea, his lawyer had said that he was 19 years old at the time of the incident and that his socio-economic background should have been considered by the court.

Earlier this month, a court in Delhi ruled that Sharma, Singh, Akshay Thakur and Pawan Gupta would be executed at 5.30 am on March 20. This was the fourth time the court issued death warrants for the convicts. The death warrant was issued a day after Kovind rejected the mercy petition of Gupta, the last of the four death row convicts.

The death warrants for the four convicts were first issued for January 22, and then postponed to February 1 because of the mercy pleas filed by two of the convicts. After this, they were scheduled to be hanged at Tihar Jail in Delhi on March 3 at 6 am, but another mercy plea led to a postponement.

The four men, and two others, raped and brutally assaulted a 23-year-old physiotherapy student in a moving bus in Delhi on the night of December 16, 2012. The woman died of her injuries two weeks later at a hospital in Singapore. The incident triggered huge protests in the Capital and across the country. One convict died in prison, while a minor convict was sent to a detention home for juveniles and was released in December 2015.