The two companies have been battling over patents related to smartphone and tablet computer technology, including features like using a double tap top zoom and the bounce back that occurs at the end of a page. Apple had filed a lawsuit last year demanding $2.5 billion and Samsung followed with a countersuit for $399 million. The jury did not award Samsung any damages in the countersuit.
Apple lawyers successfully convinced the jury that the company's patents were unique intellectual property and that Samsung, the world's largest maker of phones running on Google's Android operating system, copied them for financial gain.
It is likely Apple will ask for an injunction on Samsung products, forcing them to stay off the market until they change their designs.
Court observers were surprised at how quickly the jury reached a verdict. Many had not expected a verdict until next week, especially given that there were over 100 pages of juror instructions. The nine jurors left the federal courthouse Friday evening without talking to reporters.
Samsung is expected to appeal the decision.
The two companies are involved in similar lawsuits in several other countries. Friday, a South Korean court came to an opposite outcome, saying Samsung did not copy Apple and it was Apple that copied Samsung's technology.