The D.C. Council, frustrated by roadblocks in its investigation of possible ethics violations by member Jack Evans, voted 12 to 1 this week to allow city officials to ask a court to compel the lawmaker’s private clients to cooperate.

The lone dissenting vote was cast by Evans.

It was one of several votes taken by the Ward 2 Democrat that have pertained to investigations of his conduct in office.

The idea of recusal — that the lawmaker should decline to act on a matter that would directly affect him — was never broached by Evans or his colleagues on the D.C. Council during Tuesday’s vote.

Council rules give lawmakers discretion to decide when to sit out votes. But critics say Evans had an obvious and jaw-dropping conflict.

“He very clearly and openly voted in his own interests,” said Amber Harding, a local advocate for homeless people. “It’s hard for me to imagine this happening in any other scenario, where an employee would have a say in their own discipline or a criminal defendant getting a vote on a jury on their own conviction.”

Evans, the council’s longest-serving member, is the target of a federal grand jury investigation. Among other things, he is under scrutiny for appearing to use his council position to solicit employment from law and lobbying firms, and for receiving money and stock shares, which he says he returned, from a sign company that benefited from legislation he promoted.

Earlier this year, Evans voted against launching an internal council probe of his conduct.

He backed a nominee to the city ethics board, which had been investigating him. Evans even cast the deciding vote that allowed him to keep his committee assignments when the council moved to punish him in July.

Craig Holman, a lobbyist for the watchdog group Public Citizen, said Evans’s votes on the council investigation are especially disturbing after documents showed the veteran lawmaker attempted to stymie a separate Metro investigation of his conduct when he recently served as the transit agency’s board chairman.

“He can rig the investigation,” Holman said. “We’ve seen Jack Evans over the course of the last few years actively try to derail or influence investigations involving his scandals. That just shows every reason to believe that if he has an opportunity to get involved in matters affecting his own investigation, he will try derailing or influencing the course of that investigation.”

Holman said the D.C. Council could stop Evans from voting on his own investigation by changing legislative rules to prohibit lawmakers from taking action “that directly and substantially affects that member.”

Current rules define a conflict of interest as taking actions “likely to have a direct and predictable effect” on the financial interests of the lawmaker or a “close associate.” Recusals are uncommon.

In neighboring Maryland, state lawmakers do not vote on their own reprimands or censures.

But D.C. lawmakers routinely vote on their own disciplinary crackdowns. The late former council members Jim Graham and Marion Barry voted against their punishments in ethics scandals earlier this decade.

D.C. Council Chairman Phil Mendelson (D) did not return a request for comment Wednesday but has previously said that Evans is under no obligation to recuse.

“The fact is, he’s a member, so he gets to vote,” Mendelson said in July after Evans voted to protect his committee assignments.

Even Evans’s harshest critics on the council did not take issue with his vote Tuesday on the measure asking D.C. Superior Court to enforce subpoenas issued by the council in its Evans ethics investigation.

Mendelson said the legislation was necessary because several of Evans’s consulting clients refused to talk with lawyers from an outside firm hired to conduct the probe. Evans said Tuesday that he opposed the bill because he opposed the original resolution authorizing the probe.

He did not return a request for comment Wednesday.

Council member Mary M. Cheh (D-Ward 3) said she did not think Evans needed to recuse himself from that vote. “It’s simply asking, even though the matter involves him, should this law firm as an extension of the council have certain authorities to enforce subpoenas?” Cheh said. “That’s a more generic kind of question.”

Council member Elissa Silverman (I-At Large) said the reason she did not object was that “I knew that it would pass easily.”

Silverman and Cheh said Evans should not vote on future punitive measures, especially once the council decides what steps to take after the internal probe.

“Given that council member Evans is under investigation by several entities, having him vote on his own discipline — even if it’s not in violation of our rules — just makes us look like we are either covering up for him or unable to police ourselves,” Silverman said.

Council member Robert C. White Jr. (D-At Large) said that Evans’s action on the internal probe “deteriorates our credibility as a body” but that lawmakers had limited options to stop him. “The Council cannot prevent Councilmember Evans from voting without action from an ad hoc committee,” White said in a statement. “Until then, the responsibility falls squarely on Councilmember Evans.”

Other council members did not return requests for comment.

Some critics said the council has damaged the public’s trust by allowing Evans to repeatedly vote on the investigation.

“If he doesn’t even recuse himself on the most obvious conflict of interest, you can’t trust him to recuse himself on anything,” said Laura Fuchs, a teachers union activist. “I can’t really trust our council has any mechanism to hold anyone accountable if they are clearly ignoring his constant conflicts of interest.”