This episode's headline: Execution by injection. The guests include HENRY SCHWARZSCHILD, ACLU; ERIC FREEDMAN, Defense Attorney; In Dallas (Facilities: KERA-TV): STEVE CHANEY, Fort Worth Prosecutor; CAPPY EADS, National District Attorneys Association. Byline: In New York: ROBERT MacNEIL, Executive Editor; In Washington: JIM LEHRER, Associate Editor; LEWIS SILVERMAN, Producer; GORDON EARLE, MAURA LERNER, Reporters