A U.S. magistrate ruled yesterday that there is probable cause to believe that three Washington-area men were "in business of taking wagers."

Judge Elsie Munsell made that decision after hearing testimony from an FBI agent who supervised a gambling "sting" operation earlier this year. While the hearing was largely a formality, it probably will lead to grand-jury indictments of Daniel Snyder, George Orfanos and Kenneth Boehm.

Agent Ronald D. Kemp testified that for five months the FBI had operated a purported "layoff service" to handle bets from other bookmakers. Snyder, Orfanos and Boehm all bet with the FBI informant, but Kemp said he inferred from the "size and frequency" of the waters that the men were actually bookies.

The agent said the defendants also had made remarks that suggested they were bookies, not just bettors. In one instance, Kemp said, Snyder told the FBI informant that he couldn't pay his debts because he hadn't collected from his own customers.

But the agent could not cite any cases when the defendants actually had taken bets.

"How many wagers did Mr. Orfanos accept?" attorney Plato Coacheris demanded.

"From whom" Kemp asked.

"From anybody."

"None."

Kemp said the FBI had seized Snyder's personal papers in a search of his apartment and concluded from them that he was " at least at the level of a bookmaker." But his further testimony indicated that if Snyder was a bookmaker, he was an uncharacteristically unprrosperous one. Four times he had settled his debts to the "sting" operation with personal checks, for sums of $900 or less. All four checks bounced.

"Isn't it true that Mr. Snyder is a deadbeat?" defense attorney Joel Finkelstein asked.

Kemp assented.Scrutiny of Snyder's finances had suggested that he never seemed to have any money, a condition Finkelstein suggested was more often associated with betting rather than bookmaking.

"Do bookmakers ordinarily pay off with bad checks," he asked Kemp.

"No," the agent replied.

Prosecutor Karen Tandy said a grand jury indictment "is a routine step after a probable-cause hearing." If that indictment is handed down shortly, the case probably would go to trial within three months or so.