Apple faces a hefty legal bill after a jury found it guilty of using technology owned by a US university without permission. The licensing arm of the University of Wisconsin claims Apple’s A7 chip infringes on a patent it filed in 1998.

Apple denied the accusations and argued that the patent is invalid, Reuters reported. It had previously tried to convince the US Patent and Trademark Office to review the patent’s validity, but in April the agency rejected this bid.

According to Reuters, the iPhone maker could face up to $862 million in damages for infringing on a patent that improves chip efficiency.

The University’s non-profit patent management body, Wisconsin Alumni Research Foundation (WARF), sued Apple in January 2014, claiming Cupertino infringed on WARF patents with its A7, A8, and A8X processors, which are found in the iPhone 5s, 6, and 6 Plus, and the iPad.

The court must decide how much Apple must pay.

WARF last month filed a second lawsuit against Cupertino over its newer A9 and A9X chips, which are in the next-gen iPhone 6s, 6s Plus, and iPad Pro.