North's show is over, but key questions remain. His testimony under immunity makes it hard for Walsh to prosecute

Mounting a successful prosecution against Lt. Col. Oliver North, following his performance in congressional hearings, will be extremely difficult, says former Watergate special prosecutor Charles Ruff. The question, Mr. Ruff says, is whether the Iran-contra special prosecutor, Lawrence Walsh, has facts other than those disclosed by Colonel North under questioning in the joint House-Senate hearings.

Prosecutor Walsh is saddled with the inability to use testimony by North, compelled under a grant of ``use immunity'' by the congressional committees. Mr. Walsh and his staff cannot even develop leads from that testimony.

``The issue is not, can he prosecute,'' says Ruff, ``but can he convince a court that the case he puts on hasn't been tainted by North's testimony.''

North has acknowledged lying to Congress to help maintain the contra war in Nicaragua. In addition, he admitted to accepting a home security system worth $13,800, which was paid for with government funds, then writing fake letters to cover up that fact. North testified that he prepared false chronologies of events and admitted to shredding documents right under the noses of Justice Department officials.

In his interim report, Walsh indicated the difficulties he faces: ``It is sometimes suggested that the experience of the Watergate prosecutions demonstrates that congressional grants of use immunity do not significantly impede successful prosecutions. This is very misleading. If anything, the Watergate experience demonstrates the contrary. Although two immunized witnesses in the Watergate matter - John Dean and Charles Colson - subsequently pleaded guilty, no immunized Watergate witness who refused to plead guilty was successfully tried and convicted.''

If indicted, North could face charges of conspiracy, obstruction of justice, and misuse of public money.

Although acknowledging the difficulty he faces, Walsh has taken steps to protect his prosecution.

First, he expedited parts of his investigation which he thought were most likely to involve matters that would be disclosed under congressional immunity.

Second, the independent counsel developed and used a filing procedure to preserve evidence in a demonstrably ``untainted'' form.

This means that before immunity becomes effective, the independent counsel gathers pertinent evidence and possible leads, seals them, and lodges them with the court. This procedure helps establish an independent origin for evidence.

Third, Walsh has insulated the lawyers and investigators concerned with prosecution of individuals under immunity from the immunized testimony produced in the congressional hearings. Other lawyers are designated as an ``exposed'' team, familiar with the immunized testimony. This team is necessary, says Walsh, for liaison work with government agencies and the select committees, and to monitor hearings for possible perjury.

Georgetown University law Prof. Paul Rothstein says that even with the ``Chinese wall'' Walsh has constructed, he will have trouble picking an unbiased jury. ``Every man, woman, and child in this country has been watching [the Iran-contra hearings] and making up their minds. This was a master stroke by Brendan Sullivan [North's attorney] to buck the Congress and insist that all this testimony be public.''

Richard Ben-Veniste, who was chief of the Watergate task force, says that if the special prosecutor makes it over the tainted-testimony hurdle and selects a jury, he will still be faced with convincing the jury of North's criminal intent.

``He [North] certainly helped himself a great deal [in the hearings]. He is an articulate witness. The sincerity of his views made people believe he engaged in authorized conduct.''

North says he was following orders from the late director of central intelligence, William Casey, and other superiors. Senate counsel Arthur L. Liman refers to this as the ``Nuremberg defense.'' (Defendants in the Nuremberg war crimes trials after World War II claimed they were only following superiors' orders.)

Another stumbling stone for the prosecution is what Mr. Ben-Veniste terms ``graymail,'' as opposed to blackmail - sensitive national-security documents essential to North's defense but volatile to American foreign policy.

Professor Rothstein says North can ``hold a gun to the head of the United States by saying that `in order to exercise my constitutional right to put in evidence on my behalf, I have to reveal secrets.''' Rothstein adds that ``nine out of 10'' times in these situations, the prosecution is dropped.

He adds that even if nobody goes to jail, ``we did learn an awful lot about how government is mixed up on allocations of foreign policy power.''

Rothstein calls the nationally televised hearings ``a big town meeting'' that will, at the very least, produce new laws governing the way foreign policy is made and executed.

In the article yesterday on special prosecutor Lawrence Walsh, it was incorrectly stated that a home-security system accepted by Oliver North worth $13,800 was paid for with government funds. The system was paid for by North associate Richard Secord, who was in charge of the covert airlift to resupply the contras.