The Federal U.S. Circuit Court of Appeals in Washington, D.C., on Friday upheld a federal judge's legal definition of Apple's so-called "quick links" patent at issue in the dispute between Apple and Motorola.
Apple accuses Samsung of infringing the patent, which allows users to send phone numbers directly to a device's dialer.
The appeals court ruling extended the monthlong trial by at least a day, and jurors could begin deliberations Tuesday afternoon or Wednesday morning.
The high-stakes battle between the world's largest smartphone makers has exposed the cutthroat competition between the two companies. Each company accused the other of ripping off designs and features. At stake: $2 billion if Samsung loses, a few hundred million if Apple loses.
Teams of attorneys on both sides have spent the month trying to poke holes in obscure and bureaucratic patent legal claims, while keeping the eight jurors engaged. Drawing the most attention in the courtroom and the media are insider emails and meeting presentations documenting the frustration each company faced as they competed for market share.
Less than a year after Apple unveiled its iPhone in 2007 combining a web browser, music player and phone in one touch-screen device, Samsung officials noted they were quickly losing customers.
But Samsung fought back, using Google's Android system, offering less expensive smartphones with larger screens.
Both have studied each other's marketing as well.
In 2009, Samsung designers examined step by step why iPhones were known to be easier to use than Samsung, finding their own offerings lacked emotion and charm.
When Samsung aired a Super Bowl ad in 2013, Apple marketing head Phil Schiller had praise for the competition.
"It's pretty good and I can't help but think, `these guys are feeling it' (like an athlete who can't miss because they are in a zone) while we struggle to nail a compelling brief on iPhone," he wrote in an email. "That's sad because we have much better products."
Throughout the three years of litigation, Samsung's market share has grown. One of every three smartphones sold last year was a Samsung, now the market leader. Apple, with a typically higher price, was second, with about 15 percent of the global market.
Although it's impossible to predict what a jury will do, two years ago a federal jury found Samsung was infringing on Apple patents. Samsung was ordered to pay about $900 million, but it is has appealed the judgment and has been allowed to continue selling products using the technology.