Conversations on wiretaps of John Anthony Walker Jr.'s telephones and evidence seized in searches of his house, plane, cars, hotel room and safe deposit box may be used at the trial of the accused Soviet spy, a federal judge ruled here today.

U.S. District Judge Alexander Harvey II refused to dismiss the case because of what defense lawyers described as massive prejudicial publicity between Walker's May 20 arrest and his May 28 indictment on espionage charges along with his son, Navy Seaman Michael Lance Walker.

Harvey said there was no precedent for taking such a step and that a transcript of the grand jury proceedings revealed no evidence that the jurors had been unduly swayed by reports about the case.

The judge said he will wait until the trial to rule whether continuing publicity about the case makes it impossible for Walker to obtain a fair trial and requires dismissal of the charges.

"This is not the time for taking any such action," Harvey said.

In the second of two days of pretrial hearings, Harvey upheld the legality of wiretaps on Walker's house, boat and three business telephones. The wiretaps, which were authorized April 5 by the secret Foreign Intelligence Surveillance Court, continued until Walker's arrest.

He said the government had demonstrated "ample probable cause" for obtaining nine warrants for searches of Walker's house and the Rockville hotel room where he was registered at the time of his arrest and for various other possessions. Those included film and software seized at Walker's house and a Manila envelope, containing detailed instructions for leaving packages at a Montgomery County "drop site," that allegedly fell from Walker's pocket when FBI agents arrested him.

Meanwhile, lawyers for three men awaiting trial on espionage charges -- John Walker, Michael Walker and retired Navy communications expert Jerry Alfred Whitworth -- said they will present their cases before juries rather than before a judge alone.

John Walker's older brother, Arthur James Walker, opted to have his case heard by federal Judge J. Calvitt Clarke Jr., who last week found the retired Navy lieutenant commander guilty of seven counts of espionage.

With a jury, "We have twelve chances of somebody saying, 'No, I don't believe the government's evidence,' " said John Walker's lawyer, federal public defender Fred Warren Bennett. He said he will not seek a change of venue for the trial, which is scheduled to start here Oct. 28. Harvey agreed Thursday to separate the trials of father and son, and he said Michael Walker will be tried soon after the end of his father's trial