What constitutes an intentional act by appellant in refusing to testify before a grand jury?

The majority reasons that appellant's "intentional acts" place him in a position similar to that of an escapee or a parolee who commits offenses which lead to revocation of his parole. Even those do not authorize a sentencing court to change the sentence originally imposed on the initial offense. But appellant's fault is of a different order from an escape or parole violation. His refusal to testify before the grand jury does not come within the McDonald v. Lee exception because it is not the fault of a prisoner qua prisoner; rather, it is an act totally extraneous to his imprisonment. In contrast to the other transgressions cited by the majority, appellant's refusal to testify does not evince any intent to avoid or terminate service of his sentence. Moreover, his silence before the grand jury is an "intentional act" only in an oblique and technical sense. Appellant displayed every intention of serving his term promptly and continuously; any argument that he willfully interrupted his sentence is sophistical.