WASHINGTON (AP) _ The name of Washington lawyer Thomas C. Green has popped up so often in the Iran-Contra hearings that Sen. Warren Rudman, R-N.H., said Tuesday that testimony so far ''raises the question of whether he was a lawyer or a participant.''

Green's conduct was questioned anew during questioning on Tuesday of Fawn Hall.

Earlier, he spent four days at the hearings at the side of his client, Richard V. Secord, the retired Air Force major general who managed the business enterprise that sold arms to Iran and the Nicaraguan Contras.

At different times, testimony has indicated, he also represented Secord's business partner, Albert Hakim, and Oliver L. North - the former National Security Council staffer who directed the clandestine Iran-Contra operations. Miss Hall was North's secretary.

In addition, according to various witnesses and documents:

-It was Green who met with Secord, North and Hakim last Nov. 24, just as Attorney General Edwin Meese III was learning of the secret Contra operation and was about to expose it in a public announcement. The refusal of participants to testify about the meeting, citing attorney-client privilege, has led some lawmakers to wonder aloud whether the subject was a cover-up.

-Green received at least a $40,000 ''finder's fee'' after linking up Secord with an arms supplier so the weapons could be sold to the Contras at a time U.S. government lethal aid was banned.

-When North held a ''shredding party'' to destroy key documents in his office last November 21, it was Green's name that appeared on North's calendar for a meeting that followed the incident.

-When Miss Hall left her boss' office Nov. 25 with secret documents under her clothes and in her boots, it was Green who accompanied her and North out of the building. According to Miss Hall, Green did not tell her to take the documents back after he learned she had them.

And when Miss Hall said she would give a misleading answer if asked about the shredding, Green - according to Miss Hall - said, ''Good.''

''The record will be viewed - has been viewed - by the independent counsel,'' Rudman said, noting that it's not up to Congress to decide whether charges are warranted.

There also are ethical rules, approved by the District of Columbia Court of Appeals, that apply to attorneys practicing in Washington. These include disciplinary rules that can result in punishments.

For instance, the rules state a lawyer shall not engage in conduct involving dishonesty, fraud, deceit or misrepresentation; or conduct prejudicial to the administration of justice.

Thomas Henderson, bar counsel for the D.C. Bar and the prosecutor in disciplinary cases against lawyers in the capital, said he can initiate an investigation if he believes there may have been an ethical violation.

But he said the investigation stage is confidential, and would not say whether this case would be ripe for such a probe.

A lawyer's fate in the city is eventually decided by the District of Columbia Court of Appeals.

Green did not return a reporter's telephone calls seeking comment on Monday and Tuesday.

However, Earl Silbert, Green's lawyer, told The Washington Post that, ''Mr. Green has always been ready to respond to any questions about his conduct.''

''His ability to do so has been restricted by the attorney-client and other privileges and constitutional rights. And he has followed the advice of his counsel,'' Silbert said.

The Post, in Wednesday's editions, quoted informed sources as saying that Green refused to testify in April before a federal grand jury investigating the case. He invoked his claim of attorney-client privilege and his Fifth Amendment right against self-incrimination, Silbert said.

Sen. David Boren, D-Okla, questioned Miss Hall Tuesday about Green's role on Nov. 25, when she left North's office with the documents.

The key parts of the exchange went this way:

Boren: ''And during this time, did Mr. Green indicate to you that you should not be taking these documents out?''

Miss Hall: ''No, sir. Mr. Green didn't comment on any of what was going on except as I said later about the shredding.''

Boren: ''Now, so he didn't, in any case, indicate to you, he didn't say anything to you like, 'Miss Hall, as a lawyer, I should tell you that you might be in some jeopardy for taking these documents out,' or 'You should take them back and turn them back over to the security director.' Did he give you any kind of advice at all about taking the documents back?''

Miss Hall: ''No, sir.''

Boren: ''Now he also discussed with you, I believe in that same, in the car at the same time, after you were giving the documents to Col. North, he did discuss the shredding with you, didn't he - Mr. Green?''

Miss Hall: ''Yes.''

''And he asked you what you were going to say if you were asked about them, is that correct?''

''Yes.''

''And you said, 'We always shred documents.'''

''Yes.''

''And Mr. Green indicated to you that he'd be pleased with that answer, is that correct?''

''I believe he did.''