Lawyers for Apple Inc. and Samsung Electronics Co. kicked off their high-stakes patent infringement trial last week on a day marked by drama and tension. Much is at stake. Apple seeks $2.5 billion from Samsung for allegedly stealing features of the iPad and iPhone.

But even if the jury awards Apple that much money, the company likely would face an uphill battle making the award stick. As recent high-profile patent trials have shown, big awards often evaporate or shrink drastically in post-trial motions and appeals.