Who is wrong? The snooper or the cheater?

Wonderer89
You see this fairly often here, the girl has gone through her partners phone because she was suspicious.
Everyone generally jumps on her for invading his privacy, which of course is true but what if she finds out he was actually cheating? Is her behaviour then justified as he most likely wouldn't have been caught otherwise?
Who is wrong in this scenario, if you had to pick one?

*swap the gender scenario if relevant
The snooper
The one hiding information
Select gender and age to cast your vote:
Who is wrong? The snooper or the cheater?
65 Opinion