A federal judge in Florida has harpooned a key legal defense that 3M planned to use against thousands of lawsuits accusing the company of knowingly making defective earplugs used by U.S. soldiers.

Maplewood-based 3M has denied the allegations and invoked the "government contractor defense," which shields contractors from tort liability for defects in products designed and developed for the federal government. 3M has claimed that the earplug in question was designed in close collaboration with the military.

But U.S. District Court Judge M. Casey Rodgers ruled Friday that there was insufficient evidence "to establish the elements of the government contractors defense" by 3M.

"The [earplug's] design already existed — it came into existence without any input from the Army," Rodgers wrote in the ruling. "The Army never issued a request for a design proposal for the new earplug, there was no competitive bidding process during which the Army established design details for a new earplug from interested contractors."

The lawsuits piling up in Florida — many from war veterans who said they have suffered hearing loss — stem from the Combat Arms or "CAEv2" earplug, which a company called Aearo Technologies began selling to the U.S. Army in the late 1990s. 3M bought Aearo in 2008 and continued to sell the earplug until just a few years ago.

3M said in a statement the company is reviewing its options and continuing discovery in the case.

3M’s CAEv2 earplugs were designed to block all noise if the green end was inserted into the ear or block damaging noise but allow “low-level commands” if inserted on the yellow end.

"We remain confident the evidence will show that the CAEv2 product, which was developed in response to the U.S. military's request and based on its own specifications and testing, was not defective and did not cause injuries," the statement said.

A statement from plaintiffs' attorneys said they were "pleased the court rejected 3M's attempt to blame our nation's military for its defective earplugs that have permanently damaged the hearing of hundreds of thousands of service members. 3M's own internal e-mails and testimony show how the company was aware its earplugs were defective" and "failed to inform the military."

Combat Arms earplugs were supposed to give users two options for hearing protection. The wearer could insert the green end of the earplug into the ear to significantly block all sound. If the user inserted the yellow end of the plug into the ear, critical "low-level" commands — but not loud, damaging noises — could be heard in the field, according to 3M.

Plaintiffs said Aearo and 3M knew the earplugs were not long enough and did not work properly as designed.

Mike Hughlett • 612-673-7003