Oliver North, the self-acknowledged "action officer" of the Iran-Contra affair, went

on trial Tuesday facing 12 criminal charges arising from his role in the worst scandal of the Reagan administration.Nine women and three men chosen as jurors were sworn in by U.S. District Judge Gerhard Gesell to hear the case against North.

Lead prosecutor John Keker, in a 90-minute opening statement, said North placed himself above the law by allegedly lying to Congress in 1985 and 1986 about his actions in support of the Nicaraguan Contra rebels.

Keker also said the government's first witness Wednesday will be Rep. Lee Hamilton, D-Ind., who was chairman of the House Intelligence Committee and of the special House panel that investigated the Iran-Contra scandal in 1987.

Keker said a host of others involved in the affair would also be government witnesses, including former Attorney General Edwin Meese; North's former secretary, Fawn Hall; and Robert McFarlane, ex-national security adviser.

But North's chief defense lawyer, Brendan Sullivan, in his opening statement, said his client "worked in a secret world" at the National Security Council and never had any criminal intent when he kept his activities shielded from Congress.

"Ninety percent of his work was secret," Sullivan said, "and he always acted with the approval of his superiors" at the White House.

The opening statements began a courtroom drama that has been 11 months and $15 million in the making - and could last as long as five months.

About three dozen people, on hand to witness history, lined up outside the courtroom an hour before the trial began. Independent prosecutor Lawrence Walsh won North's indictment March 16, 1988, on charges arising from the 1985-86 sales of U.S. arms to Iran and the diversion of profits to the Contra rebels in Nicaragua.

North faces 12 counts of lying to Congress, destroying official documents, tax fraud and accepting illegal gifts. If convicted on all counts, he could be sentenced to 60 years in prison and fined $3 million.

Among the District of Columbia residents sitting in judgment of the former National Security Council aide are a Labor Department statistician, a retired bus driver, a hospital laboratory technician and a World War II veteran who served under Gen. George Patton.

The jury, empaneled Feb. 9 after eight days of laborious questioning, was not sworn in until Tuesday because the administration hurriedly entered the case with complaints about Gesell's rules for the handling of classified information at trial.

An angry Gesell sent the panelists home to await a resolution to the complaints, which the administration took to the Supreme Court.

Walsh and Attorney General Dick Thornburgh then devised a plan that gives Walsh the lone responsibility for handling the secrets in the courtroom but reserves for Thornburgh the power to prohibit the use of the secrets.

Should Thornburgh exercise that power, Walsh could be forced to drop some or all of the charges against the retired Marine lieutenant colonel.

The sheer complexity of the case long threatened to prevent a trial - and the complications could prevent the jury from ever returning a verdict.