I had also heard that about the direction of eyes when someone is lying or trying to remember something etc. So I went to look it up. This may be more info than anyone wants, but it's interesting considering our search for the truth.
Look Both Ways Before Answering
Pupil size isn’t the only way your eyes communicate. The direction in which someone looks while talking can also speak volumes. As you’re probably aware, the brain is divided into two hemispheres. The left hemisphere is primarily responsible for logic and analytical thought, while the right hemisphere is where emotional and creative thinking occur. Because the right brain governs the left side of the body and vice-versa, we tend to look to the left when using our right brains and to the right when using our left brains.
Recalling existing information is largely a right-brain task, which means that when we’re trying to remember something we usually look to the left. Conversely, we typically look to the right when trying to construct a description or a story, making use of the logical powers of the left brain. To make matters even more interesting, looking upward suggests that a person is using images or visual memories. Looking downward is associated with kinesthetic or emotional memories, while looking directly left or right usually means the person is processing auditory data.
I’ve read in several places that because looking to the right means a person is constructing something new, this implies lying. But I’ve also read exactly the opposite—that looking to the left suggests lying (presumably because the creative right brain is being used). Still others claim that whichever direction you associate with lying, you have to switch it if the person is left-handed! In reality, the association between gaze direction and truthfulness is a tenuous one. Making up a new sentence doesn’t necessarily involve making up a new fact, after all. And although left-handed people are slightly more likely to be right-brained than right-handed people, one’s dominant hand doesn’t necessarily have anything to do with one’s dominant brain hemisphere. All the same, law-enforcement personnel are regularly taught to take note of a suspect’s gaze direction during an interrogation. Although eye movement is much less foolproof than a polygraph, it can suggest areas in which someone is not being entirely forthcoming.
That's interesting albeit inconclusive. I guess being shifty eyed would be the real clincher. You look left to try to remember what your story was supposed to be, then you look right when you're asked a question which you weren't prepared for and have to use then creative side of your brain, then left again to try to come up with some logic to make sure that new part of your story fits into the picture.