UPDATE: Jury raises Costco damages bill to $13.75m

Costco has been hit with punitive damages of $8.25m for selling engagement rings that infringed Tiffany & Co's trademarks.

The decision comes less than a week after the jury said Costco should be liable for $5.5m in compensatory damages linked to the profits the retail wholesale chain made from the sale of the rings. Costco claimed it had made only around $781,000 in profit from the rings.

Costco was tight-lipped on the latest decision, saying in a statement: "Proceedings are continuing. Because the jury's verdicts will be subject to further consideration by the court, further comment is not appropriate at this time." That suggests the company is planning to appeal the ruling.

Tiffany sued Costco three years ago, saying that Costco had engaged in counterfeiting and deceptive business practices, among other things. The court rejected Costco's counterclaim that Tiffany is a generic term for a particular style of engagement ring setting.

"We felt a responsibility to protect the value of our customers’ purchases and to ensure that Costco‘s customers were not misled about their purchases," said Leigh Harlan, Tiffany's general counsel. "It is critically important that the Tiffany name not be used to sell any engagement ring that is not its own."