两术语均为《美国联邦宪法》所禁止的法律，都属于剥夺犯有严重罪行，如treason或felon等罪犯公民权利的一种专门立法，对法令规定之犯罪者可不经审判即处以惩罚。区别在于bill of attainder ( “极刑惩处法”)(也称为act of attainder)规定不经审判即可适用死刑[1] ；而bill of pains and penalties ( “严刑惩治法”）规定的处罚则相对较轻，不包含死刑[2]。《美国联邦宪法》是将 bill of pains and penalties 归并在 bill of attainder 中一起加以禁止的。

[1]“A special legislative act prescribing capital punishment, without a trial, for a person guilty of a high offense such as treason or a felony. ”Cf. Bryan A. Gamer, Black's Law Dictionary, 7th edition, at p. 159, West Group (1999).
[2] "An act is a bill of attainder where the punishment is death and a bill of pains and penalties when the punishment is less severe; both kinds of punishment fall within the scope of the constitutional prohibition. " Cf. The Publisher's Editorial Staff, Black's Law Dictionary, abridged 6th edition, at p. 114, West Publishing Co. (1991 ).