A district court has the authority to correct an obvious drafting error in a patent, the U.S. Court of Appeals for the Federal Circuit has ruled, reversing a judgment invalidating the affected patent claim.

On Aug. 10, a unanimous panel in in CBT Flint Partners LLC v. Return Path Inc. reversed a July 2008 summary judgment ruling by Judge Thomas Thrash Jr. of the Northern District of Georgia. Thrash had ruled that a claim in a patent owned by CBT Flint Partners was invalid for indefiniteness, believing that he was not authorized to correct the error. By that time, the claim was the only one left in CBT’s infringement suit.

In August 2007, Software developer CBT sued e-mail technology company Return Path and the Cisco IronPort Systems LLC, which is part of Cisco Systems Inc., alleging infringement of 10 claims in one patent and one claim in a second patent that involved methods for charging a fee for sending spam e-mail.

Cisco developed the allegedly infringing e-mail analysis system and later sold it to Return Path.

After court proceedings on the patent claims, the parties stipulated that the defendant did not infringe the 10 claims of one of the patents.

Judge Alan Lourie authored the Federal Circuit opinion, joined by Judges William Bryson and Richard Linn.

At issue was a phrase centering around the words “detect analyze” in the following section of the patent claim: “the computer being programmed to detect analyze the electronic mail communication sent by the sending party to determine whether or not the sending party is an authorized sending party or an unauthorized sending party.”

Lourie wrote that “the district court erred in this case by holding that it was not authorized to ‘correct’ the supposed…error.”

“Specifically, the district court failed to recognize that the claim contained an obvious error, which is confirmed by the fact that a person of skill in the art would find the claim to have the same scope and meaning under each of the three possible meanings that the court found reasonable,” Lourie wrote.

The district court’s first reasonable and possible interpretation, deleting the word “detect,” works because the system would have to detect an e-mail before analyzing it, Lourie wrote.

Lourie moved on to the lower court’s second reasonable and possible interpretation, to delete the word “analyze.” He concluded that such an interpretation would not change the scope of the patent claim because there’s also language requiring the system to “determine whether or not the sending party is an authorized sending party or an unauthorized sending party.”

Lourie then wrote that the district court’s third reasonable and possible fix, to add the word “and” between the words detect and analyze, “corrects an obvious error.”

“Because each of the three proposed reasonable interpretations would result in the same claim scope, requiring that the computer be programmed to “detect and analyze” the e-mail, a person of skill in the art would readily know that the meaning of the claim requires insertion of the word “and” between the words ‘detect’ and ‘analyze,’” Lourie wrote.

Bruce Baber, a partner at Atlanta’s King & Spalding and one of CBT’s lawyers, said the firm doesn’t comment on pending litigation. Michael Council, who owns Cordele, Ga.-based CBT, also declined to comment.

Return Path and Cisco IronPort’s lawyers at Philadelphia’s Duane Morris did not return calls for comment. Cisco declined to comment. In a statement, Return Path spokesperson Erica Manney said the company “continues to believe that this lawsuit has no merit and [is] confident that the end results out of the legal system will confirm that.”

Kenneth Bressler, a New York partner at Philadelphia’s Blank Rome who was of counsel on the brief for Return Path and Cisco IronPort declined to comment.

Erik Belt, a Boston intellectual property partner at McCarter & English, who isn’t involved in the case, said the ruling is “good news for patent owners.”

“It tells courts you can exercise your common sense to fill in the blanks when there’s an obvious typo or error in printing the claim,” Belt said. “The mere fact that a claim may have some sort of typo or missing word does not necessarily invalidate the claim.”

If the patent owner noticed the error when it was first issued, it would have been relatively easy to get a certificate of correction from the U.S. Patent and Trademark Office, Belt said.

“The whole dispute and thousands and thousands of dollars in legal fees could have been avoided,” Belt said.

Sheri Qualters can be contacted at squalters@alm.com.