Published on Monday, June 24, 1991
© 1991 The Arizona Republic

The clue that turned the case was a microchip, a tiny piece of a triggering device to detonate a bomb.

 From it, U.S. and Scottish investigators found a new trail that refuted the conclusions of almost two years of arduous legwork by thousands of agents worldwide - and eventually changed major assumptions about the downing of Pan Am Flight 103 over a small Scottish village just four days before Christmas 1988.

 A key breakthrough, which came just as the largest international criminal probe in history neared an impasse, was almost a fluke. A ''brilliant young CIA analyst,'' as one insider describes him, decided to try a new hypothesis: Could someone besides the widely suspected culprits - Palestinian radicals, their Syrian patrons or Iranian militants - have been involved?

 The analyst started with a hunch.

 He searched for a ''signature'' that would match the Pan Am bombing with earlier incidents to prove his suspicions. Culling CIA files, he came up with the 1984 bombing of a French UTA airliner in Chad. A premature explosion blew up the baggage compartment while the plane was still on the ground and wounded 27 persons.

 He also found a link with an attempt in 1986 to blow up the U.S. Embassy in Togo. Officials in Lome, the Togolese capital, had arrested nine people with two suitcases full of plastic explosives.

 But the biggest find was an obscure case in Senegal involving the arrest of two men at Dakar's airport in February 1988. They possessed 20 pounds of sophisticated Semtex plastic and TNT explosives, weapons and several triggering devices.

 The analyst's hunch was right.

 In all three cases, the ''signature'' was distinctly Libyan.

 In Senegal, the two men who were arrested - Mohammed Marzouk, alias Mohammed Naydi, and Mansour Omran Saber - were agents of Libyan intelligence. And the triggering devices in their possession matched the microchip fragment from the Pan Am bomb.

 The connection since has provided a new set of answers to the ''who,'' ''where,'' ''how'' and ''why'' involving Pan Am 103's blowing up over Lockerbie, Scotland.

How the case now looks
Based on the forensic breakthrough and the links with earlier cases, investigators now believe that:

 --> The regime of Moammar Gadhafi carried out the bombing. Libyan intelligence, headed by Abdullah Sanussi, orchestrated the plot.

 --> The primary motive was revenge for the 1986 U.S. bombing of Tripoli, the Libyan capital, in which about 40 people, including Gadhafi's adopted daughter, were killed.

--> The mysterious bag carrying a bomb-laden Toshiba radio-cassette player on the blown-up Pan Am 103 came from Malta. The bomb was probably flown on an Air Malta flight to Frankfurt, Germany - although the passenger and cargo log has disappeared. In Germany, the cassette player was loaded on Pan Am 103 as an interline bag, unattached to any passenger.

 Vital missing pieces in the puzzle finally fell into place. The breakthroughs mean that, unlike a half-dozen unsolved terrorist cases against U.S. targets in the 1980s, the bombing of Flight 103 may go to court.

 Assistant Attorney Gen. Robert S. Mueller III, who heads the Department of Justice's Criminal Division, appears poised to take the case to a grand jury, according to U.S. officials.

 Should the grand jury return sealed indictments, the biggest obstacle may not just be arresting those involved. U.S. authorities already are working with French police seeking to apprehend one of the Libyan suspects somewhere in North Africa.

Early suspects
The new evidence on the Pan Am bombing, which began to emerge last summer, contradicted the longstanding belief that the crime was linked to the Popular Front for the Liberation of Palestine-General Command headed by Ahmed Jebril. The radical group, based in Syria, is outside the PLO umbrella.

 The original case was based on the arrest of a cell of 16 operatives in Germany two months before the 1988 bombing. The group was found to have five sophisticated bombs, especially designed to blow up aircraft, hidden in electronic equipment.

From his base in Damascus, Jebril also was known to have worked closely with Iran, where he frequently traveled. Investigators believed that Tehran commissioned the Popular Front to target an American plane in retaliation for the accidental 1988 U.S. downing of Iran Air Flight 655 over the Persian Gulf in which 290 people died.

 The crucial clues that changed the direction of the probe were the detonators. The Popular Front's detonators were all Czech-made. They were attached to altimeter devices that were set to go off once a plane reached a certain altitude.

 But, as forensic experts discovered, the detonator fragment that was culled from the wreckage of Flight 103, which had been scattered over 845 square miles of Scottish countryside, had important discrepancies.

 It was of Swiss manufacture - from the same company that had made the triggering devices that were found on the Libyan agents in Senegal. And it was attached to an ordinary timer that had been set to go off at a certain hour.

 The ''fingerprint'' of the Pan Am bomb was identical to the devices carried by the Libyan agents who were caught in Senegal.

 Unfortunately, Senegal freed the Libyan agents, who were never formally charged, in June 1988. U.S. officials believe that their release was part of a package deal in exchange for Libya's ending support for Senegal's opposition forces and for restoring diplomatic relations between the two countries, which had been severed eight years earlier.