Apple's iPhone and iPad violated three of Samsung's patents, an expert witness for the South Korean company testified on Tuesday as the company went on the offence in the third week of a high stakes trial.

Dr Woodward Yang, an electrical engineering professor at Harvard, said Apple's products had implemented Samsung-patented features, such as the process for seamlessly emailing photos, or easily finding photos in an album.
He was one of Samsung's first witnesses after a parade of Apple experts accused Samsung of similar infringements last week.
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 US 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.
On Tuesday, Yang said Samsung's patents were filed before the introduction of the iPhone in 2007.
He focused on patents that cover smartphone features, not wireless technology.
In an attempt to invalidate some of Apple's patents in the case, Samsung 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.
(Editing by Gary Hill)