Dr. Woodward Yang, an electrical engineering professor at Harvard, said Apple's products use Samsung-patented features for mobile devices, including the process for seamlessly emailing photos. He was one of Samsung's first witnesses after a parade of Apple experts said Samsung phones and tablets violated Apple's patents.

Additionally, one of Samsung's designers testified that she did not rely on Apple designs to create icons for Samsung's Galaxy S smartphone line.

Apple and Samsung are going toe-to-toe in a patents dispute mirroring a struggle for industry supremacy between two rivals that control more than half of worldwide smartphone sales.

The U.S. company accuses Samsung of copying the design and some features of its iPad and iPhone, and is asking for a sales ban in addition to monetary damages. The Korean company, which is trying to expand in the United States, says Apple infringed several patents, including some for its key wireless technology.

Apple concluded presenting evidence regarding its own patents this week, and Samsung started calling witnesses. On Tuesday, Yang said Samsung's patents were filed before the introduction of the iPhone in 2007.

Yang focused on patents that cover smartphone features, not wireless technology. One of those patents covers technology for easily finding photos in an album.

"The idea here was, let's have a bookmark," Yang said.

Under questioning from Apple attorney Bill Lee, Yang acknowledged he had not seen evidence that Samsung actually used any of those features in its own smartphones.

Later on Tuesday, Samsung called designer Jeeyuen Wang, who said she and a large Korean team worked hard for three months to create Samsung's own icon designs for Galaxy S phones.

"I slept perhaps two hours, or three hours a night," Wang said.

Apple attorney Michael Jacobs showed Wang internal Samsung documents - with her name on them - containing references to Apple icons. However, under questioning from Samsung attorney John Quinn, Wang said some of those documents were created well after Samsung had finished its own designs.

In an attempt to invalidate some of Apple's patents in the case, Samsung also presented evidence this week to show that Apple's patents cover technological advances -- like multitouch -- that had already been developed before Apple claims to have invented it.

The case in U.S. District Court, Northern District of California, is Apple Inc v. Samsung Electronics Co Ltd et al, No. 11-1846.

(Reporting by Dan Levine; Editing by Gary Hill, Bernard Orr)

• A Permanent Economic Emergency