I wouldn't put it past (someone)

Based on that person's pattern of behavior, it is not impossible to imagine them engaging in that kind of bad behavior. Do I think Joe stole the money? Honestly, I wouldn't put it past him. He has no conscience. It seems a bit far-fetched that the government is spying on us with our own appliances, but I wouldn't put it past them. He's a very charming guy, but I wouldn't put it past him to stab me in the back if it meant advancing his career.

wouldn't put it past someone

If you say that you wouldn't put it past someone to do something bad, you mean that you would not be surprised if they did it. He wouldn't put it past Caitlin to have stopped work and gone home for the night, even though she knew how important it was.

I wouldn’t put it ˈpast somebody (to do something)

used to say that you think somebody is quite capable of doing something surprising, unusual, etc: ‘Do you think he’d ever steal from his friends?’ ‘I wouldn’t put it past him.’