In 2007, when Apple unveiled the iPhone, Samsung was still best known for its flat-panel televisions. Since then, Samsung has rocketed to the top of the smartphone world in terms of sales and units shipped and sparked an epic technological — and legal — rivalry. In courtrooms around the world, Apple and Samsung are squaring off over mobile device patents. The skirmishes began in 2011, and today some 40 lawsuits still hang in the balance. The next battlefield is San Jose, where a trial in the Northern District of California begins on March 31.