Federal prosecutors issued a vigorous rebuttal yesterday to defense contentions that accused spies John Walker Jr. and his son Michael cannot receive a fair trial because of a deluge of publicity about the case.

"The amount of publicity has reflected the legitimate public interest in the facts and nature of the case, as well as its significance to related issues of national security," Assistant U.S. Attorney Michael Schatzow said in a motion filed in U.S. District Court in Baltimore.

Schatzow's motion also said that publicity about Walker, 47, a retired Navy warrant officer and communications expert, and his 22-year-old son, who had been serving as a seaman on the aircraft carrier USS Nimitz, did not appear excessively harmful in light of past court decisions.

News items about the Walkers have been "neither inflammatory nor unduly prejudicial in the context of the type of publicity which has resulted in reversals of convictions," Schatzow said in the motion.

The two Walkers are charged in the case along with John Walker's brother, Arthur, and Jerry Alfred Whitworth, who has been described as a friend of John Walker Jr. John Walker has been depicted as the leader in the alleged espionage ring, which authorities say passed defense secrets to the Soviets.

Lawyers for John Walker and his son have moved to dismiss the charges against their clients on grounds that publicity prejudiced the grand jury and that no jurors could be found who have not been influenced by pretrial publicity.

In his motion, Schatzow said the defendants "cannot point to any prejudice or bias in any member of the grand jury, let alone in enough grand jurors to vitiate the indictment."

He also denounced possible leaks of information by government officials who are outside the law enforcement community but have received information about the case because of their positions and its importance.