Washington, DC (AP)  -- Sen. Arlen Specter wants an independent investigation of the Patriots' taping of opposing coaches' signals similar to the Mitchell Report on performance enhancing drugs in baseball.

Specter again criticized the league's handling of the investigation and threatened the possibility of revoking the NFL's antitrust exemption during a news conference Wednesday. The senior Republican on the Senate Judiciary Committee met with former New England video assistant Matt Walsh a day earlier.

NFL commissioner Roger Goodell indicated he considered the investigation over after meeting with Walsh on Tuesday.

"Everybody pooh-poohs it," Specter said. "It's ridiculous to make that kind of contention."

Specter, from Pennsylvania, cited the fact a Patriots attorney sat in on Walsh's meeting with Goodell as proof the investigation has not been impartial.

He repeated his disapproval of Goodell's decision to destroy the notes and tapes confiscated during the initial investigation last fall.

"That sequence is incomprehensible," Specter said. "It's an insult to the intelligence of the people who follow it."

If the NFL condones cheating, Specter said, it encourages others to cheat.

"They owe the public a lot more candor and a lot more credibility," he said.