The same clause of the Constitution which prohibits bills of attainder, declares that no ex post facto legislation shall be passed.
In the early case of Calder v. Bull10 the prohibition was declared to relate only to criminal and not to civil proceedings, and, as thus limited, ex post facto laws were declared to be " every law that makes an action done before the passing of a law, and which was innocent when done, criminal; and punishes such action. Every law that aggravates a crime, or makes it greater than it was, when committed. Every law that changes the punishment, and inflicts a greater punishment, than the law annexed to the crime, when committed. Every law that alters the legal rules of evidence, and requires less, or different testimony, than the law required at the time of the commission of the offense, in order to convict the offender."
By later decisions this definition of ex post facto legislation has been broadened so as to include all laws which in any way operate to the detriment of one accused of a crime committed prior to the enactment of such laws.11
6 4 Wall. 333; 18 L. ed. 366.
7 Justices Miller, Swayne, and Davis dissented in both the Garland and Cummings eases.
8 Martin v. Snowden, 18 Gratt. 100.
9 In re Yang Sing Hee, 13 Saw. 486.
10 3 Dall. 386; 1 L. ed. 648.
11 In Thompson v. Utah (170 U. S. 343; 18 Sup. Ct. Rep. 620; 42 L. ed. 1061), the more important adjudications with reference to this subject are summarized as follows: " It is sufficient now to say that a statute belongs to that class [of ex post facto laws], which by its necessary operation and 'in its relation to the offense, or its consequences, alters the situation of the. accused to his disadvantage. (United States v. Hall, 2 Wash. C. C. 366; Kring v. Missouri, 107 U. S. 221; 2 Sup. Ct. Rep. 443; 27 L. ed. 506: Medley, Petitioner, 134 U. S. 160; 10 Sup. Ct. Rep. 384; 33 L. ed. 835.) Of course a statute is not of that class unless it materially impairs the right of the accused to have the question of his guilt determined according to the law as it was when the offense was committed. And. therefore, it is well settled that the accused is not of right entitled to be tried in the exact mode, in all respects, that may be prescribed for the trial of criminal cases at the time of the commission of the offense charged against him. Cooley in his Treatise on Constitutional Limitations, after referring to some of the adjudged cases relating to ex post facto laws, says: 'But so far as mere modes of procedure are concerned, a party has no more right, in a criminal than in a civil action, to insist that his ease shall be disposed of under the law in force when the act to be investigated is charged to have taken place. Remedies must always be under the control of the legislature, and it would create endless confusion in legal proceedings if every case was to be conducted only in accordance with the rules of practice, and heard only by the courts in existence when its facts arose. The legislature may abolish courts and create new ones, and it may prescribe altogether different modes of procedure in its discretion, though it cannot lawfully, we think, in so doing, dispense with any of those substantial protections with which the existing law surrounds the person accused of crime.' Chap. 9, § 272. And this view was substantially approved by this court in Kring v. Missouri, above cited. So, in Hopt v. Utah (110 U. S. 574; 4 Sup. Ct. Rep. 202; 28 L. ed. 262), it was said that no one had a vested right in mere modes of procedure, and that it was for the State, upon grounds of public policy, to regulate procedure at its pleasure. This court, in Duncan v. Missouri (152 U. S. 377; 14 Sup. Ct. Rep. 570: 38 L. ed. 485), said that statutes regulating procedure if they leave untouched all the substantial protections with which existing law surrounds the person accused of crime, are not within the constitutional inhibition of ex post facto laws. But it was held in Hopt v. Utah (above cited), that a statute which takes from the accused a substantial right given to him by the law in force at the time to which his guilt relates would be ex post facto in its nature and operation, and that legislation of that kind cannot be sustained simply because, in a general sense, it may be said to regulate procedure. The difficulty is not so much as to the soundness of the general rule that an accused has no vested right in particular modes of procedure, as in determining whether particular statutes by their operation take from an accused any right that was regarded, at the time of the adoption of the In Thompson v. Missouri12 the authorities are again reviewed, the court in this case holding that a state statute authorizing the comparison of disputed handwriting with any writing proved to be genuine is not an ex post facto law in its application to crimes previously committed, as altering the legal rules of evidence in existence at the time of the commission of the offense.