Ruling Smeargle portrait confusion

[phalt]

Just a quick question I've searched for but not found an answer (probably because I didn't look hard enough!)

If my opponent is 100% certain I have no support cards (and I do not have any) in my hand, can he still use portrait to look at my hand?

Happened a few weeks ago at Regionals and I should have called a judge over at the time to clear it up.
It's been bothering me ever since!

 

[Captain Pidgey]

Yes, he can. I don't know why he would, but he still can.

 

[Riskbreakers]

He'd probably do it just to see what are the cards phalt has in his hand lol.

 

[CarlosDuranJr]

they can do it, would likely do it because they forgot what was in your hand. it'a LAO nice way to distract you and maybe get in your head a little bit.

but they are allowed to because the contents of your hand and deck are not public knowledge.