It's shown inmates get their DNA registered when they are admitted to Blackgate. This means BATMAN'S DNA is on public record!!
It may entirely be possible Hugo Strange used the oddity of Malone and Batman being at Blackgate at the same time as a clue to help him find this record. If he found out Malone was Bruce Wayne, finding a Batman connection wouldn't be impossible.
It may entirely be possible Hugo Strange used the oddity of Malone and Batman being at Blackgate at the same time as a clue to help him find this record. If he found out Malone was Bruce Wayne, finding a Batman connection wouldn't be impossible.