US resident who unknowingly cast illegal vote in 2016 was deported

This is wild. I didn’t realize that could actually happen by mistake. How does someone even "unknowingly" cast a vote if they aren't a citizen? Is there something on the registration form that makes it confusing, or do they just get tricked at the polls?

That Reuters data analysis really puts things into perspective compared to the headlines we usually see. It's wild how one mistake can lead to something as extreme as deportation. Do you think more people are unaware of the rules, or is this just a rare slip-up?