Ken Balcomb says new pictures of the brain of a harbor porpoise that died in Puget Sound last May are very telling.

The pictures show signs of severe trauma.

"This is another smoking gun for me that we've got a consistent trauma here," says whale researcher Balcomb.

Balcomb says the evidence convinces him that Navy sonar killed the porpoises.

Government scientists examined 11 porpoises that washed ashore. But they won't release any evidence until all the lab results are in. They tell KOMO 4 News that will take at least two more months.

But Congress plans to decide next month whether to exempt the Navy from the Marine Mammal Protection Act.

Balcomb says, "I'm concerned that the design of the whole investigation is intended to slow things down."

The investigation should tell us if Navy sonar killed the 11 porpoises. The USS Shoup used sonar on a training exercise off San Juan Island.

In a rare coincidence, whale researchers using underwater hydrophones, recorded the sound and its effect on killer whales.

Within days, dead porpoises started washing up.

Three months later, the National Marine Fisheries is still investigating.

Navy Lt. Bill Couch says, "The Navy is very interested in the results, we are sensitive to the plight of marine mammals in Puget Sound so it's important to wait for those final results."

National Marine Fisheries says its investigation into the porpoise deaths is completely separate from the congressional debate over marine mammal protection.

But Balcomb believes the government should know what killed the porpoises before it decides whether to allow the Navy to ignore rules protecting marine mammals.