At a second round of Senate Judiciary Committee hearings yesterday the witnesses were 3 to 1 against Chairman Strom Thurmond's (R-S.C.) bill to reinstitute the death penalty for some federal crimes.

But Thurmond, after saying the committee wanted to hear all sides, remained only long enough to hear the International Association of Chiefs of Police endorse his bill and then departed, leaving only Sen. Arlen Specter (r-Pa.) to hear opposing arguments from Sen. Carl Levin (D-Mich.), the American Civil Liberties Union and the U.S. Catholic Conference.

Norman Darwick, testifying for the police association, said most law enforcement officials strongly believe the death penalty serves as a deterrent to crime, though he conceded that statistics on the subject are unreliable.

The bill would permit the death penalty to be imposed for treason, espionage and murder convictions in federal courts. When Specter noted that this would not apply to the great majority of homicides committed outside federal jurisdiction and tried in state courts, Darwick said he doubted that many persons would understand the distinction.

Levin, once a public defender official in Detroit, said one of several reasons to oppose capital punishment is that it makes it impossible to correct a mistake.

The ACLU opposes the bill as "unnecessary, unwise and unconstitutional." It said the Thurmond bill fails to meet the Supreme Court's requirement that the death penalty can be imposed only in a manner that is not arbitrary or discriminatory. The ACLU said the bill violates a long-established rule that would require a unanimous jury vote to impose the death penalty. The bill provides for a special post-conviction proceeding which, at one stage, permits a finding by a majority vote of the jury.

The most Rev. ERNEST nterkoefler, bishop of Charleston, S.C., opposed the bill for the U.S. Catholic Conference. As a former prison chaplain who had been present as six men were sent to the electric chair, he said: "I can assure the committee that capital punishment is brutal and inhumane. It is also final. Judicial error can never be corrected." The bishop also testified that capital punishment unfairly discriminates against the poor, who cannot afford the best legal defense.