SANTA ANA, Calif. — A federal jury on Thursday rejected Mattel’s claims that it owns the copyright to the blockbuster, billion-dollar Bratz doll line and instead awarded upstart rival MGA Entertainment more than $88 million in damages for misappropriation of trade secrets.

The verdict came as a staggering blow to the toy giant, which has long claimed the smaller company stole the idea for the ethnically diverse, pouty-lipped toys that gave platinum-haired Barbie a run for her money after decades of fashion doll dominance.

The jury, which deliberated for nearly two weeks after a three-month trial, also found that Mattel acted willfully and maliciously in misappropriating MGA’s trade secrets. That raises the possibility the judge could also add on punitive damages, attorneys for both sides said.

The verdict will allow MGA to regain control of its doll and to once again try to compete with Mattel’s Barbie doll, said MGA attorney Jennifer Keller.

“If Mattel had won this lawsuit, MGA would have been wiped out, and that’s what Mattel wanted to do,” she said.