Hesitation and other unauthorised information - Laws 16 and 73
While playing a hand, you and your partner may only communicate about it through bidding and playing cards. Any other communication about it breaches the Laws. You may not use information from your partner's comments, reactions or gestures during bidding or play.
If unauthorised information is given, it is a breach of the Laws. The Laws say you must ignore it, and bid or play as if you had not received it. There will be a presumption that the information guided you, unless it is clear that you acted naturally without referring to it.
If your partner hesitates for a long time, then passes, you know she has a hand which might justify a bid. You don't have to pass, and it is in order to make a call if you would clearly make the same call if your partner did not hesitate. If you would otherwise pass or make some other bid, then you must pass or make that bid.
Some hands need thought. There is usually less problem if you hesitate then bid something, other than pass. However, sometimes any hesitation may give unauthorised information.
One more example. You lead a suit, and your partner glares at you. You have received unauthorised information that it was the wrong suit. If your natural action is to lead that suit again, then you must do that, ignoring the information you have received.
Copyright Michael O'Malley 2016
(Other examples of potential unauthorised information that have sometimes made the news include, but are not limited to, Dummy tapping the table next to a particular suit or touching cards that declarer has not called for; a player placing their hand on the table during bidding with a specific number of fingers displayed; folding a hand of cards before the auction is finished; placing a group of cards on the table when arranging the cards; and the old reliable, which may be apocryphal, of rubbing the ring finger to indicate diamonds!.) Obviously, none of these are allowed.