wouldn't put it past someone

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.
See also: past, put

not put (something) past (one)

1. To believe one is capable of doing something unsavory, immoral, illicit, selfish, etc. 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. I should know by now not to put such vile treachery past the likes of him.
2. To be unable to swindle, fool, or deceive one. My grandmother might be 85, but you still can't put a thing past her! That sleazy used car salesman couldn't put his bogus little scam past me.
See also: not, past, put
Farlex Dictionary of Idioms.

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.
See also: past, put, someone
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • I wouldn't put it past (someone)
  • I wouldn't put it past somebody
  • hardball
  • code of practice
  • practice
  • sexual misconduct
  • on a slippery slope
  • slippery slope
  • slippery slope, a
  • the slippery slope