Herbert O. Reid Sr., legal counsel to Mayor Marion Barry and his point man on a host of recent controversies, has emerged as a key figure in the defense of University of the District of Columbia President Robert L. Green against claims that he misspent thousands of dollars of university funds, according to university sources.

Reid, who was appointed by Barry to the 15-member UDC board a year ago and who, according to some, is a leading candidate to become its new chairman, is helping Green prepare his response to a critical draft report by D.C. Auditor Otis H. Troupe. The report concludes that the president misspent $14,000 of university funds on travel, consulting and flowers sent to personal friends.

The Washington Post also has reported that UDC records show that Green has billed the university for travel to funerals and a wedding, as well as for $80,000 of catering and nearly $18,000 of household expenses since he took office in September 1983.

The trustees are scheduled to meet tonight to review Green's official response to the findings and criticisms, which UDC administration officials have been working on feverishly for the past week.

Several well-placed sources said that Reid, a well-known civil rights lawyer and former acting dean of the Howard University Law School, is helping the embattled Green to orchestrate his defense and launch a counteroffensive. Reid was appointed to an ad hoc committee of the board of trustees to respond to questions posed by a D.C. City Council committee about the university's finances.

Reid is also responsible for reviewing all UDC documents before they can be released to news organizations that have asked for them under the D.C. Freedom of Information Act. UDC has a freedom of information officer, assistant general counsel Joseph A. Julian, who until several weeks ago handled such inquiries.

Reid refused yesterday to discuss his role in the UDC controversy with a reporter.

A UDC spokesman said he saw no conflict in Reid's serving simultaneously as a trustee and an adviser to Green during this controversy, even though the board has oversight responsibility for the university. A spokesman for Barry said that Reid's activities at UDC have no relation to his function as the mayor's lawyer. Several high-ranking UDC officials, who declined to be identified, said that Reid has taken a leading role in defending Green primarily to avoid having to mount another lengthy search for a new UDC president. Green, 51, is the third president of UDC in eight years.

"Herb Reid is a very trusted and valued adviser to the president, a member of the board of trustees who has had a long association with the president," said UDC spokesman Gilbert Maddox in explaining Reid's involvement with Green during the seven-week-old controversy.

Maddox said Reid had consulted with Green during preparation of the response to the auditor, but that he had not been involved in "the minute details."

Maddox said Green had asked Reid to review university records before they are released to the press because of Reid's "legal expertise and because he is one of the outstanding lawyers in this country."

Green's report to the trustees tonight will be his first formal attempt to explain his expenditures of UDC funds. Ronald H. Brown, the current chairman of the board whose term expired last year, also helped in preparing the carefully crafted report, according to knowledgeable UDC sources.

Sources close to the board said that some members have become frustrated with Brown's role in handling the controversy and say that the chairman has done little to determine whether Green has misappropriated university funds.

Privately, these board members have expressed their support for trustee Joseph Webb, who this week said Green should be placed on administrative leave and should resign if he can't disprove the auditor's allegations.

Meanwhile Brown has been lobbying board members to vote for Reid for chairman, according to UDC sources.

"Clearly Herb has been programmed and polished," said one source close to the board. "If you look at the long-term political implications, the mayor made the decision to appoint Herb Reid because he knew he could not reappoint Ron Brown as chairman."

Maddox said that Green may hold a news conference later this week "depending on the decision of the board and what they want."

According to sources close to the board, Reid and trustee N. Joyce Payne are the frontrunners for the chairmanship. The board may vote on a new chairman tonight.

Reid became an influential player on the board shortly after taking office in July 1984 and has maintained a close alliance with Brown.

Earlier this year, Reid traveled to Minnesota to take depositions in a sexual harassment suit filed against Green by two employes of the Minnesota Commission on Human Rights. The suit stems from an incident in Minneapolis last year in which the women alleged that Green harrassed them when they came to his hotel room to escort him to an evening event where he was supposed to speak.

Brown said in an interview two months ago that he had asked Reid to monitor the case for the board of trustees, even though the incident occurred while Green was traveling on personal business. UDC paid for Reid's trip to Minnesota, according to documents obtained under the freedom of information law.

Reid also has taken a leading role in defending Barry in a number of controversies, including a federal grand jury investigation of drug use by city employes in which the mayor was linked to Karen Johnson, a former city worker and convicted cocaine dealer.