Trial about to begin in suit alleging covert-action conspiracy. Left-wing group depicts a shadowy network operating before Iran-contra

One of the grandest conspiracy theories of the American Left will get its day in court here next week. In a politically loaded civil suit, the left-wing Christic Institute has alleged the existence of a long-running conspiracy that directed covert American operations in Central America.

This secret, ready-made network, Christic lawyers allege, trafficked in drugs and weapons and plotted political assassinations in support of the Nicaraguan contras. And this, they add, was only the latest venture in three decades of dirty work around the world, all with the back-door sanction of United States officials.

The plaintiffs in the case claim the right to civil damages under a federal racketeering law. But observers of various political stripes have asserted that all or part of Christic's case is stretched a bit thin over their evidence.

But if they can prove their case in court, says Jay Winik, an aide to last summer's congressional Iran-contra committee and now a visiting fellow at the Center for Strategic and International Studies, ``the policy and political implications would be amazing.''

The $17 million suit names 29 people, including contra leader Adolfo Calero, retired US generals Richard Secord and John Singlaub, arms trader Albert Hakim, and former Central Intelligence Agency employees. Christic avoided naming any government officials, such as Oliver North, spokesman Peter Dykstra says, because of the legal protections that the government might invoke.

Because the case is civil, not criminal, the Christics need to show only that their claims are supported by a ``preponderance'' of the evidence - i.e., that their evidence is more convincing than that offered by the defense.

At the heart of the case is the 1984 bombing of a press conference at La Penca, Nicaragua. The bomb was apparently an attempt to murder Ed'en Pastora G'omez, then leader of a contra faction. Instead, eight people were killed, and free-lance cameraman Tony Avirgan, on assignment for ABC, was wounded and his camera equipment destroyed.

Mr. Avirgan and his journalist wife, Martha Honey, are the actual plaintiffs in the suit.

After the bombing, Avirgan and Ms. Honey traced the bombing, they say, to a conspiracy centered around John Hull, an American rancher in Costa Rica active in supporting the contras. Mr. Hull sued the couple for libel in Costa Rica and lost.

The lead counsel for the institute, Danny Sheehan, had already assembled a much larger tapestry of alleged conspiracy dating back to anti-Castro operations in 1959 and heroin transshipment in Southeast Asia during the Vietnam war.

In Avirgan and Honey's situation, Mr. Sheehan saw grounds to get the whole alleged enterprise into court.

Frustration at official indifference

Avirgan says that he and his wife were reluctant to launch their legal battle because it hampered their journalism careers, but they were increasingly frustrated with official indifference to the La Penca incident.

In Sheehan's narrative web, Avirgan says, they saw the larger pattern that fit their La Penca theory.

In a telephone interview from his Costa Rica home, Avirgan admits that he and Honey ``have sometimes been uneasy'' with the deductive leaps in the Christic case. Lawyers, especially Danny Sheehan, are sometimes willing to reason to conclusions where journalists ask for proof, he says. But the couple has come to view that as ``creative tension.''

``We feel quite at ease going into the trial,'' he says.

Allegations by `David'

The primary evidence that ties the La Penca bombing to the defendants is the story of an alleged defector from the conspiracy, known only as David, who told his story to a Costa Rican restaurateur, Carlos Rojas Chinchilla. David himself was kidnapped and killed, according to Costa Rican authorities.

David - through Mr. Rojas's story - is also the principal source for another major allegation in the case: that the defendants conspired to assassinate Lewis Tambs, then US ambassador to Costa Rica, collect the $1 million bounty on his head offered by Medell'in cartel cocaine smugglers, and blame it on Nicaragua's Sandinista government.

Jes'us Garc'ia, a former Dade County police officer who has been convicted on gun-possession charges, also claims to have attended meetings plotting against the ambassador where the defendants were described as participants. Attacks on witnesses' credibility

The case alleges extensive trafficking in cocaine to help finance the contras. These charges rest primarily on the testimony of pilots now convicted of drug smuggling who claim to have flown drugs for contra support networks.

Tom Spencer, General Singlaub's lawyer, vows to, ``as we say in Miami, make piccadillo'' of the credibility of these witnesses.

Mr. Spencer calls Carlos Rojas ``a real nut'' who cried through much of his 23-hour deposition. And Spencer claims that Ram'on Mili'an Rodr'iguez, a convicted drug-money launderer who has testified about drug cartel ties to the contra supply network, has cut a deal with Democrats: testimony against current administration figures in exchange for help in obtaining an early prison release.

The Christic Institute will not get to paint as broad a canvas as it would like to in this case. Federal District Judge James King has limited the plaintiffs' evidence-gathering scope to the period 1982-86 and to Central American ventures.

Limits on evidence gathering

Christic attorney Lanny Sinkin says that the limits on discovery will not weaken the case, but only weaken ``our ability to show the jury how serious and dangerous this group is.''

But the discovery limits also push Christic's overall target - three decades of allegedly tainted CIA covert operations - largely out of range.

Still, asserts Mr. Sinkin, the suit will be able to show that a secret team existed long before Oliver North tapped into it and ``that there is a national security apparatus outside the law that engages in criminal enterprises.''

The conservative Council for InterAmerican Security has taken on the debunking of the Christic suit as a special project. The council's concern is that other political groups will follow the Christic Institute's lead in using the civil racketeering laws to become ``private attorneys general.''

The suit has driven General Singlaub to the verge of bankruptcy, his attorney says, and taken all of his time for two years - keeping him from his work of supporting anticommunists around the world.

The lawyers expect the trial to last about six months. The judge is seeking a pool of 500 candidates for drawing an unbiased six-member jury.