Samsung made its most compelling argument yet on why Apple's '381 bounce-back patent shouldn't be consider valid, with an expert witness providing a lengthy look at the Tablecloth application we saw this week. Dr. Andries van Dam, a faculty member at Brown University since 1965, walked the jury through the elements specified in the '381 patent, each of which appeared to be met by the application — and in his opinion, rendering the patent invalid due to prior art.

Tablecloth runs on the DiamondTouch Table computer, and as demonstrated yesterday allows a user to scroll through an image — in the example shown, a pair of desktop images — and then displays a blank white space when the user reaches the end; removing a finger causes the image to snap-back, much like Apple's feature. Tablecloth dates back to 2005, while Apple's bounce-back patent was originally filed in December of 2007.

Dr. van Dam also demonstrated the user interface LaunchTile. As demonstrated yesterday, LaunchTile didn't appear to be similar to the '381 patent because when a user reaches the end of the on-screen content there is no off-screen information revealed. However, van Dam said that the software does meet the requirements when swiping within the main content field itself, the next next tile serving as the "off-screen content" in this case.

In fact, van Dam said that the US Patent Office had never seen the two pieces of software before granting Apple its patent. "I examined the prosecution history," he said, "and there is no mention of these two pieces of prior art."

Apple offered a relatively mild response, first pointing out that Tablecloth returns the user to the original starting point upon a bounce-back, rather than the edge of the content; van Dam replied that the patent doesn't actually describe what the point of return should be. The company then focused on whether the DiamondTouch Table was legitimately a "touchscreen device" as specified in the patent. The DiamondTouch consists of a projector that shoots visuals down upon a capacitive screen, rather than having the display and touch-sensitive surface combined as in the iPhone and iPad. Apple's attorney tried to thread the needle as to what the definition was of a touchscreen truly was, but van Dam didn't budge. "The patent does not tell you how you implement a touchscreen display," he said, explaining that it only describes the behavior of the user interface. The DiamondTouch certainly qualified underneath the patent language, he said. "In every way that is a touchscreen display."