Apple's patents are key to their legal successes against Samsung and other companies. But what happens when one of those patents is ruled invalid? Well, not only does Apple lose the right to sue over that patent, any patents based upon that patent could also be ruled invalid.

The patent that Steve Jobs is best known for, 7,479,949, has been preliminarily ruled invalid. The patent covers a touchscreen device and input derived from apply heuristics. The patent, if you speak legal and engineering, probably does a better job explaining than I can:

A computer-implemented method for use in conjunction with a computing device with a touch screen display comprises: detecting one or more finger contacts with the touch screen display, applying one or more heuristics to the one or more finger contacts to determine a command for the device, and processing the command. The one or more heuristics comprise: a heuristic for determining that the one or more finger contacts correspond to a one-dimensional vertical screen scrolling command, a heuristic for determining that the one or more finger contacts correspond to a two-dimensional screen translation command, and a heuristic for determining that the one or more finger contacts correspond to a command to transition from displaying a respective item in a set of items to displaying a next item in the set of items.

Two months ago, Apple was also told that the its patent covering the rubber-banding effect was invalid. This ruling came months after Samsung was fined $1 billion, partly on the basis of this patent. With Samsung appealing, we could see Samsung actually coming out a victor, or at least not so far behind.