The US District Court of Delaware has ruled that patents owned by chip firm Rambus are unenforceable in its case against rival Micron.
US judge Sue Robinson ruled that Rambus cannot pursue its claims against Micron due to 'spoliation', as the company executed its document retention policy during a time when it anticipated litigation.
"In light of Rambus' litigation conduct, the very integrity of the litigation process has been impugned," said the judge. "The appropriate sanction for the conduct of record is to declare the patents in suit unenforceable against Micron."
Rod Lewis, vice president of legal affairs and general counsel at Micron, said: "We are pleased with the Delaware Court's ruling that the 12 patents Rambus asserted against Micron in the Delaware case are unenforceable.
"We believe that the decision is applicable to other pending cases, and we are reviewing the ruling to determine its potential impact."
Rambus has said it plans to appeal the decision. "We respectfully, but strongly, disagree with this opinion, and at the appropriate juncture plan to appeal," said Tom Lavelle, senior vice president and general counsel at Rambus.
"This opinion is highly inconsistent with the findings of the Court in the Northern District of California, which looked at the same conduct and found there was nothing improper with our document retention practices.
"We are confident in the strength of our position and will continue to vigorously pursue fair compensation for the use of our patented inventions."
The case was originally filed by Micron against Rambus in August 2000 and was then split into three separate phases.
Rambus has a raft of patent suits underway at the moment against a host of other firms, including Micron, Hynix, Nanya and Samsung in the Northern District of California.
Some of the patents included in the Delaware case are also involved in the cases in California and, as a result, Micron is filing a motion to have Robinson's ruling applied to the other cases.
Furthermore, Rambus is currently embroiled in legal proceedings against Samsung, Hynix and Micron, claiming that the companies illegally fixed Dram prices and output to eliminate Rambus' proprietary RDRAM product from the market.
That case is scheduled to start trial in the San Francisco Superior Court in March 2009.
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