Senator Joseph R. McCarthy announced Wednesday he will refuse to testify at the pending contempt-of-Congress trial of Wendell H. Furry, associate professor of Physics, unless Judge Bailey Aldrich '28 withdraws from the case.

In the strongest language he has yet employed since Judge Aldrich acquitted former Social Relations research assistant Leon J. Kamin '48 of similar charges Jan. 5, McCarthy told the Senate that "in Judge Aldrich's kangaroo court, the government has not the slightest hope of obtaining a conviction."

Calling Aldrich "a demonstrably incompetent judge," the Wisconsin Senator said his "past conduct proves that he will not rule fairly and objectively in a Communist case." He added that Aldrich's refusal to uphold the Senate's contempt citation was an insult. He said, "We should not give him an opportunity to insult the Senate again."

McCarthy's decision may force government lawyers to call off the prosecution of Furry, whose trial has been scheduled for May 21. Judge Aldrich's withdrawal from the case is most unlikely, and McCarthy would have been the government's key witness.

There was some indication before McCarthy's speech that government lawyers were considering closing the case. Several Boston newspapers printed a vague announcement last week that U.S. Attorney Anthony Julian had gone to Washington for conferences and that Furry's case might be called off as a result. Julian has announced no action.