A U.S. federal appeals court has overturned a 2011 jury decision awarding $920 million in damages to DuPont in a trade secrets lawsuit involving high-strength synthetic fibers used in products such as Kevlar body bullet-proof vests.

The case has been sent back to a district court in Virginia for further proceedings under a different trial judge.

In the verdict against South Korea's Kolon Industries dating from September 2011, the appeals court said the judge had abused his discretion and prejudiced the Korean company in granting a pretrial motion by DuPont, thus excluding evidence to Kolon's defense.

The same jury later found that Kolon had misappropriated 149 DuPont trade secrets relating to the latter's Kevlar para-aramid fiber, used to make tires, fiber-optic cables and body armor.

The appeals court said it was ruling "with reluctance," noting that Kolon and five executives were criminally charged in August 2012 with trade secret theft, after the FBI obtained what the court called "compelling evidence of Kolon's misconduct"

DuPont expressed disappointment at the decision and said it will continue to "vigorously pursue" Kolon to hold the company accountable.

Lawyers for the Korean company told the news agency Reuters, "DuPont has for decades published details about Kevlar in hundreds and hundreds of publicly available patents. A significant part of our defense is to be able to show that."

DuPont began the litigation in February 2009, claiming that Michael Mitchell, a 24-year veteran of the company, had taken proprietary information about Kevlar when he left in 2006 to start his own fibers business and later shared it with Kolon.