SAN FRANCISCO — Nasty legal battles are nothing new in the tech industry. But Apple’s conflict with the wireless chip maker Qualcomm, headed for a crucial court showdown this coming week, has a special intensity.

The two companies, once partners of a sort, now disagree about nearly everything — including which one deserves the most credit for shaping the evolution of smartphones.

Their formidable legal teams are at war on three continents, in a struggle that could affect the division of billions of dollars of smartphone profits and, perhaps, even how much consumers pay for their phones.

Now, the action moves to a federal courtroom in San Diego, where jury selection is set to begin on Monday for a trial on an Apple lawsuit and Qualcomm’s counterclaims. The chief executives of both companies are likely to take the stand.