I often look at people other than the presenter during sales pitches. I'm amazed at how often they will give away a potential problem with their looks as their presenter touches on some topic.
Once a member of our team was having a problem with something being said by our presenter in response to a question. She made a sound, starting to interrupt and it was picked up by one of the people we were presenting too. He pointed at her and said "do you have a problem with that answer?" It wasn't a huge deal, but it added a wrinkle to the presentation and is one of the reasons that I usually limit the number of people participating in sales presentations to those necessary and sufficient to lay out the information, make the organizational commitments and close the deal.