When Thomas Tucker opened his briefcase on Dec. 28 and saw that a shirtbox with $27,000 in cash was missing, he quickly telephoned Brookshire Motel in Fairfax County to see if he had mistakenly left it behind in the room he had stayed in the night before.

Tucker, who is in his mid-20s, was told that the money had been found and turned over to the Fairfax County police.

But his attorney, Philip J. Hirschkop, said yesterday that when Tucker called police "They wanted to ask him his whole life history."

Getting the money Tucker claims is his has now become so troublesome - in part because Tucker has decline to answer police questions about the cash - that he has filed suit against the police department. He is demanding that the police return the money to him and reimburse him for the interest he would be earning if the money were in a bank.

Complicating police efforts to determine ownership of the cash is the fact that about 10 other people have called police and claimed that they were the ones, who left the box of bills totalling precisely $27,000 in the motel.

Police spokeswoman Betty Bosarge said that most of the claims of people who called police, including one who said the $27,000 was part of his inheritance but could not explain how it got into room No. 15 at the Brookside, "were quickly eliminated."

Bosarge said the police ran all the serial numbers of the bills (10s, 20s, 50s, and a few 100s) through a computer and the money "came out clean." "It's not stolen money, at least not from reported sources," she said.

But law enforcement officials in other jurisdictions also called Fairfax police with tips about the money's origin and "some of these leads are still being investigated," Bosarge said.

The county's deputy police chief, Col. Kenneth R. Wilson, declined comment on the case.

The main problem in the return of the money, according to Hirschkop, is that police want to ask too many questions of Tucker, who gives his address as 1100 Grove Ave., Richmond.

"You should have heard the cacaphony of things they wanted to ask him," Hirschkop said.

Hirschkop said that when Tucker called police to claim the money they began to ask him all sorts of "peculiar questions" but Hirschkop said he could not recall what the questions were.

"Apparently they suspect criminal activity," Hirschkop said. But "the mere suspicion" of criminal activity, he said does not give police the right to ask so many questions about Tucker's background and history."

Hirschkop said Tucker is "perfectly willing to identify himself, describe how the money is packaged and prove that he paid for the motel room where it was found."

According to Hirschkop, Tucker is presently unemployed but "he used to be in real estate and he used to be a student." Hirschkop said he does not know why Tucker was carrying the cash in a shirt or box or how he obtained the money.

Bosarge confirmed that Tucker was the only one who claimed the money before stories about it appeared in newspapers.

To add to the mystery, the man who said he found the $27,000 identified by police as Charles Black, has disappeared. Black, who could claim the money if the owner is not found in 60 days, told reporters he was an employe of the motel. Motel personel said Black did not work there and has checked out of the motel.