Comment by rfonseca

The paper vote records (anomymous, of course) become the source of truth. There are very well established methods (Risk-limiting Audits - https://en.wikipedia.org/wiki/Risk-limiting_audit) that can randomly sample a small fraction of the ballots to guarantee with high probability that the electronic results are correct. Without paper records, the source of truth lies with the code that was run to receive and register the votes, and that is almost impossible to verify and fully trust.