What is the EVM-VVPAT verification issue before the Supreme Court? | Explained

The story so far: The Supreme Court on April 18 reserved its judgment on a batch of petitions seeking directions to tally Voter-Verifiable Paper Audit Trail slips with votes cast through Electronic Voting Machines during the elections. To determine the percentage of VVPAT machines’ slips that need to be counted to verify the accuracy of a poll, the ECI in 2018 asked the Indian Statistical Institute to come up with a “mathematically sound, statistically robust and practically cogent sample size for the internal audit of the VVPAT slips with the electronic result of EVMs.” Accordingly, in February 2018, the ECI decided that the VVPAT slips of one randomly selected polling station should be counted per Assembly constituency. He argued that there were “serious discrepancies… in 373 constituencies which went to polls in the first phase of the election.” He further relied on a July 2023 report of the Committee on Government Assurances which stipulated that “the Union government is yet to provide a reply for the last four years after it promised Parliament that it would obtain information from the Election Commission about possible discrepancies between the EVMs and VVPAT tally during the 2019 elections.” Highlighting that there exists a risk of manipulation, senior advocate Prashant Bhushan pointed out that both EVMS and VVPATs have a “programmable chip” and that the ECI has previously denied sharing their “source code” on the ground that they constitute the intellectual property of the manufacturers. Opposing the petitioners’ demand for 100% cross-verification of EVM votes with VVPAT slips, it pointed out that the proposal was a “regressive thought and tantamount to going back to the days of manual voting using ballot system.” “On an average, 1,000 VVPAT slips are required to be counted per polling station… The small size and special nature of the paper make the slips sticky. Backing the proposal for 100% cross-verification of EVM votes with VVPAT slips, former Chief Election Commissioner SY Quraishi said that it is essential to restore people’s confidence in the electoral process.