Samsung and Apple will square off in federal court trial over control of the US smartphone and computer tablet markets.
The trial will begin on Monday in San Jose, California, with the firms accusing each other of intellectual property rights.
Apple filed a lawsuit against South Korea's Samsung last year alleging the world's largest technology company's smartphones and computer tablets are illegal knockoffs of its popular iPhone and iPad products.
Apple is demanding $2.5bn in damages, an award that would dwarf the largest patent-related verdict to date.
Samsung counter claims that Apple is doing the stealing and that some of the technology such as the rounded rectangular designs of smart phones and tablets have been industry standards for years.
Billions of dollars of payments could be triggered from one business to the other and sales bans imposed if the jury finds one or both parties guilty.
Documents submitted and testimonies are also likely to throw fresh light on decision making processes and deals made by the two firms with others.
Together the two companies account for more than half of all the world's smartphone sales.
Despite the fact that Apple buys many of its components from Samsung, the two have failed to agree cross-licencing deals even after the courts forced their bosses to meet for talks.
The US trial is just the latest skirmish between the two over product designs.
A similar trial began last week, and the two companies have been fighting in courts in the United Kingdom and Germany.
The case is one of some 50 lawsuits among myriad telecommunications companies jockeying for position in the burgeoning $219bn market for smartphones and computer tablets.
Apple lawyers argue there is almost no difference between Samsung's products and Apple's and that the South Korean company's internal documents show it copied Apple's iconic designs and its interface.
Apple claims it is victim to seven patent breaches in addition to other trade violations.
It alleges these include copies of its designs for the bodies of the original iPhone and the iPad as well as user-interface elements such as the bounce-back response when a person scrolls beyond the end of a list, and tap-to-zoom.
Samsung denies the allegation and counter-charges that Apple copied its iconic iPhone from Sony.
It alleges that the US company changed direction after reading an interview with two of Sony's product designers and has submitted images of Apple-created concept designs featuring the Japanese company's logo to back up its claims.
Samsung lawyers noted that the company has been developing mobile phones since 1991 and that Apple jumped into the market only in 2007.
Apple will also claim that Samsung brought products to the markets which they knew were "confusingly similar" to Apple's.
The jury will hear evidence from both sides for at least four weeks.
Apple and Samsung are already scheduled to attend a separate US hearing on 20 August to discuss another patent dispute.