Federal investigators continue to build a corruption case involving key people in John Murtha’s circle. A second defendant has pleaded guilty to charges of corruption and agreed to cooperate with the prosecution in probes surrounding earmarks given by the “king of pork,” as Murtha is known. The news brings investigators closer to the inner workings of what looks like a massive conspiracy to defraud the government through its defense contracting:

A former government employee pleaded guilty Monday and agreed to cooperate in a criminal investigation of appropriations that members of Congress steer to defense contractors.

Mark O’Hair is the second defendant in the past week to begin cooperating with federal prosecutors who are looking into alleged wrongdoing by defense contractors with ties to Rep. John Murtha, D-Pa., chairman of the House Appropriations Subcommittee on Defense.

Last week, the former chief executive of a defense contractor with ties to Murtha pleaded guilty to soliciting kickbacks from a subcontractor in Pennsylvania.

In 2007, Murtha directed $4 million in federal funds to Richard S. Ianieri’s company, Coherent Systems International Corp.

O’Hair failed to disclose that he had a position as an officer of a defense contractor while he continued to work at Eglin AFB in awarding contracts. Schaller Engineering managed to get $200,000 worth of work from O’Hair, thanks to his moonlighting. He faces up to 10 years in prison for hiding his conflict of interest, which apparently led O’Hair to start cutting deals to benefit himself all over again. This case ties to Ianieri through subcontracting, apparently between Schaller and Coherent.

The feds cut deals when they get good enough information to expand their cases. What can Ianieri and O’Hair tell investigators about Kit Murtha and his connections to his brother John? It will probably take a few more shoes to fall to discover that, but so far, the case seems well-heeled enough to keep them coming.