Former Probation Commissioner John J. O’Brien pled not guilty this morning in Suffolk Superior Court to conspiracy and bribery charges but the longest shadow cast over the proceedings was by someone absent from the courtroom: former State Treasurer Timothy Cahill.

The indictment against O’Brien charges him with bribery, conspiracy to get a job for his wife by unlawful means, and campaign finance violations in connection with a scheme to land a job for his wife at the Lottery in return for hosting a fundraiser for Cahill. But Cahill hasn’t been charged with anything and a former top aide who allegedly concocted the scheme hasn’t been charged with bribery, which raises the question: Who did O’Brien bribe?

Attorney General Martha Coakley last week said the jobs-for-campaign-cash scheme was arranged by O’Brien and former Cahill aide Scott Campbell. She didn’t mention Cahill, but at the arraignment today of O’Brien and Campbell Assistant Attorney General Peter Mullin raised Cahill’s name several times.

“O’Brien agreed to sponsor a campaign fundraiser. . .pursuant to an agreement that Cahill would appoint the defendant’s wife to a position at the state Lottery,” Mullin told Magistrate Margaret Sanel. (Sanel was brought in for the arraignment because the usual Clerk-Magistrate, Gary Wilson, recused himself because he knows O’Brien from when the former commissioner worked in probation at Suffolk.)

The attorney general’s office says the fundraiser was held in Quincy, where all three men are residents, on June 23, 2005, raising $11,100 for Cahill’s campaign coffers. Mullin said that in September 2005 Cahill “did, in fact, appoint” Laurie O’Brien to a coveted customer service post in Braintree.

Yet Cahill hasn’t been charged with accepting bribes and it appears the statute of limitations has run out on that crime.

The report issued last year by special investigator Paul Ware indicated Cahill was apprised of his aides’ desire to hire Laurie O’Brien at the Lottery but nothing in the report indicates there was testimony that Cahill knew of the quid pro quo of the fundraiser.

Other than the deepening mystery about Cahill’s involvement little new information surfaced at the arraignments. O’Brien’s attorney, Paul Flavin, said afterwards that his client did nothing illegal. “John O’Brien never discussed employment [at the Lottery] of his wife,” Flavin said. “Mr. O’Brien never offered anything of value” in an effort to get his wife a job.

A statement of the case, normally filed once a defendant is arraigned, was sealed after a request by Campbell’s attorney, Charles Rankin. Mullin agreed to keep the statement secret but indicated the attorney general’s office might move to make it available to the public later.

Campbell, the former Cahill aide, also pled not guilt today to various campaign finance violations as well as participating in a conspiracy to get O’Brien’s wife a job by unlawful means.

Jack Sullivan is now retired. A veteran of the Boston newspaper scene for nearly three decades. Prior to joining CommonWealth, he was editorial page editor of The Patriot Ledger in Quincy, a part of the...