PORTLAND, Ore. — Where is Leonard Bayard?

A company registered in Oregon and bearing his name owned an executive jet the CIA is reported to have used to transport terrorist suspects to foreign countries for interrogation -- the so-called "extraordinary rendition" program.

But a retired political science professor said Bayard does not exist and news organizations and human rights groups have failed to find him.

Now the disciplinary counsel for the Oregon State Bar is pressing forward with an investigation of Portland lawyer Scott Caplan by asking him, just who is Leonard Bayard and did you represent him?

In a letter dated Thursday, the bar formally asked Caplan whether the mysterious Bayard or his company, Bayard Foreign Marketing, were -- or are -- his clients.

Mary Cooper, assistant disciplinary counsel, asked pointed questions, including: "...who first contacted you about the representation?"

"When did this contact occur? How was this contact made (e.g., by telephone, in person, by mail)?"

"Who paid you for your services? Please identify the dates that you communicated with your client."

The bar investigation resulted from a complaint filed by Michael Munk, a former Rutgers professor who now lives in Portland, Ore., who questioned whether Caplan represented a real person.

Cooper said in her letter: "Mr. Munk's complaint suggests that, in 2003, you may have knowingly registered a corporation under a false name," which, if true, could leave Caplan facing sanctions for professional misconduct.

Caplan has declined comment on the case and did not return a phone call late Friday. But he has insisted in correspondence with the state bar that he followed the law.

The Oregonian newspaper reported Caplan told it in a 2004 interview that Bayard is a real person.

In her letter, Cooper said the identity of a client does not generally fall under the lawyer-client privilege "absent peculiar circumstances."

"Accordingly, the identity of your client in this case is not privileged information and I therefore ask you: who is your client?"

Munk said he recently saw the Gulfstream V jet for sale on a website listing by a Virginia aircraft broker but the listing has been removed and the company has not returned calls or e-mail.

The CIA "extraordinary rendition" program involves the transfer or "rendition" of terror suspects to other countries for interrogation.

Human rights groups are concerned because some of the suspects have claimed they were tortured in the countries where they were sent. But U.S. officials have denied those claims.

The bar inquiry involves only Caplan.

Munk said Friday he is pleased the inquiry is moving forward.

"Now Caplan is going to have to put up or shut up," Munk said.

The bar set a Feb. 8 deadline for Caplan to respond but he could ask for an extension.