An admitted participant in the slaying of Joseph Yablonski told the jury yesterday in W.A. Tony Boyle's murder retrial that the former United Mine Workers boss gave him the order to kill Boyle's union rival.

William L. Turnblazer, a lawyer who was president of UMW's District 19 for Tennessee and Kentucky, was a surprise witness so early in the trial.

Under questioning by special prosecutor Richard Sprague, the red-faced Turnblazer said that he participated in arranging the slaying of Yablonski. The plot also led to the deaths of Yablonski's wife, Margaret, and daughter Charlotte, on Dec. 31, 1969.

Boyle was convicted in 1974 of arranging the murders, but the verdict was set aside by the state Supreme Court.

Turnblazer said he is now serving a 15-year sentence in the Federal Correctional Institution in Memphis, Tenn., for "violating the civil-rights of the Yablonskis . . . for participating in murder."

Turnblazer said that he met with Boyle and Albert Pass, the former secretary-treasurer of District 19, who was convicted of the murders, in the union's Washington, D.C., headquarters on June 23, 1969.

Turnblazer testified: "Mr. Boyle said. 'We got to kill Yablonski, or take care of him.'"