Ever since Monica Conyers, the president pro tem of the Detroit city council, pleaded guilty last week to bribery charges, our major interest here at TPMmuckraker has been in whether her husband, U.S. Rep. John Conyers, is implicated in his wife's confessed wrongdoing.

No evidence has emerged to suggest that he is -- but at a minimum, there's reason to take a close look.

A portion of the charges against Monica Conyers concerned her relationship with a local businessman, Jim Papas. The councilwoman's former top aide, Sam Riddle, who has been cooperating with the Feds, has told the Detroit Free Press that Monica Conyers and Papas set up an arrangement in which Riddle was paid $20,000 as a "consultant" -- a job for which he says he did no work -- with Monica Conyers insisting on getting half of that as a "finder's fee."

Meanwhile, Papas needed federal approval for a hazardous waste project that one of his companies was seeking to operate. And according to Riddle, after Papas hired him, John Conyers -- the veteran Democratic power-broker who chairs the House Judiciary committee -- wrote a letter to the Environmental Protection Agency in support of the project. The Free Press has a copy of the letter.

The paper adds:

Riddle said Monica Conyers told him she wanted him to deliver the letter to Papas, but changed her mind. He said he did not know if Papas ever got a copy of the letter.

"She generated the letter," Riddle said of Monica Conyers.

So the key question is whether John Conyers knew when he signed the letter that his wife had a financial relationship with Papas. As the Free Press notes, "[e]thics rules prohibit House members from contacting federal agencies on matters in which they have a personal financial interest."

There's no evidence he did know. The US Attorney's office told the Free Press: "We didn't have any evidence the congressman was knowingly or intentionally involved in Ms. Conyers' illegal conduct." And of course, members of Congress write letters on behalf of their constituents and supporters all the time.

Still, it's reasonable to ask whether John Conyers could have or should have known, before he signed that letter, that his wife and Papas -- a prominent Detroit-area entrepreneur -- had financial ties. And John Conyers' office wouldn't answer any of the paper's questions about the letter, which hardly instills confidence.

Late Update: We should have noted that, in a statement issued Friday, the US Attorney's office said:

I also want to make it equally clear that the evidence offered no suggestion that United States Representative John Conyers, Ms. Conyers' husband, had any knowledge or role in Ms. Conyers' illegal conduct, nor did the Congressman attempt to influence this investigation in any way.

The phrase "no suggestion" goes a bit further than the US Attorney's quote in the Free Press story in distancing John Conyers from any wrongdoing.