The long-running and costly legal feud between Mattel, owner of the iconic Barbie doll, and MGA Entertainment’s rival Bratz line will this week enter a potentially decisive stage in a federal court in California.

In a trial that has already lasted seven weeks, a jury will hear arguments over Mattel’s claim that the pouty and edgy multi-ethinic Bratz dolls, which took the toy industry by storm in 2001, represent a violation of its copyright, potentially opening the way for a substantial damages claim against privately-owned MGA.