If Daoud Salahuddin has in fact gained sanctuary in Iran, his successful flight will deepen the suspicions that he was helped by another government. Mr. Salahuddin has been charged with the assassination of Ali Tabatabai, the former Iranian diplomat and antagonist of the Khomeini regime, who was shot dead last month at the door of his house in Bethesda.

Mr. Salahuddin is an American, born David Belfield. Before the shooting, he had been employed by the Iranian affairs section of the Algerian Embassy -- an office staffed by Iranians over whom the Algerians seem to exercise little control. He did not come under suspicion until the day after the shooting. It would have been time enough for a person to take a flight to New York, then another to Europe and a third from there to Tehran. But to do that would have required money, a passport -- perhaps more than one -- and possibly visas.

Everything about the Tabatabai murder indicates highly professional organization. It wasn't a sudden flight of fancy. The gunman turned up neatly dressed in a postman's uniform. After the shooting, he drove off in a postal truck apparently rented for the occasion from a real postman.

Counterfeiting a passport is not impossible, but it is at least as difficult as counterfeiting money. Amateur work tends not to get beyond the immigration booths at their airports.Mr. Salahuddin was reportedly a man of some intelligence, but had no prior experience in engraving and printing.

The Tabatabai affair fits, as we have previously observed, into a wider pattern of assassinations and attempts in Europe, manifestly organized out of several Middle Eastern and North African countries embassies. In the case, the shooting was arranged by an organization that was capable of providing a postman's pith helmet, a gun and a getaway. If Mr. Salahuddin is out of the country, that organization was also able to provide a variety of false documents.

If Mr. Salahuddin actually turns up in Iran, he will be beyond the reach -- perhaps permanently -- of American justice. But it will demonstrate that he had accomplices more skillful and more experienced than the two under arrest. The next question will be the source of the fake passports.