71 U.S. 277 (1867)
The plaintiff in error, a priest of the Roman Catholic Church, was indicted and convicted in one of the circuit courts of the State of Missouri of the crime of teaching and preaching as a priest and minister of that religious denomination without having first taken the oath, and was sentenced to pay a fine of five hundred dollars and to be committed to jail until the same was paid.1
On appeal to the Supreme Court of the State, the judgment was affirmed, after which the case came before the United States Supreme Court on a writ of error to the Supreme Court of Missouri.2
The oath prescribed by the constitution of Missouri embraces more than thirty distinct affirmations or tests.3 It requires the affiant to deny that he has ever been in armed hostility to the United States or manifested adherence to the cause of its enemies, or sympathy with those engaged in rebellion, or harbored or aided persons engaged in guerrilla warfare, or entered or left the State to avoid enrolment or draft in the military service of the United States.4
Every person unable to take this oath is declared incapable of holding any office of honor, trust, or profit under the authority of the State, or of being an officer or director of any corporation, or of acting as a professor or teacher in any educational institution or school, or of holding real estate in trust for the use of any church or religious society.5 No person is permitted without taking the oath to practice as an attorney or to serve as a bishop, priest, deacon, minister, or other clergyman to teach, preach, or solemnize marriages.6
Persons holding positions at the time the constitution takes effect must take the oath within sixty days or their positions become vacant.7 Fine and imprisonment are prescribed as punishment for holding or exercising any of the specified offices, positions, trusts, professions, or functions without having taken the oath, and false swearing in taking the oath is declared to be perjury punishable by imprisonment in the penitentiary.8
Whether the test oath provisions of the Missouri constitution constitute a bill of attainder prohibited by the federal Constitution?9
Yes. The provisions presume the guilt of priests and clergymen for past acts such as entering or leaving the State to avoid enrolment or draft. They adjudge the deprivation of the right to preach or teach unless the presumption is removed by the expurgatory oath. This legislative enactment creates the deprivation without any of the ordinary forms and guards of judicial trial.12
The same result occurred when the plaintiff in error was convicted and fined for preaching without taking the oath. These features match the definition of a bill of attainder.
The test oath provisions of the Missouri constitution constitute a bill of attainder prohibited by the federal Constitution.13
Whether those provisions constitute an ex post facto law prohibited by the federal Constitution?14
By an ex post facto law is meant one which imposes a punishment for an act which was not punishable at the time it was committed. It also includes a law that imposes additional punishment to that then prescribed. Or it changes the rules of evidence by which less or different testimony is sufficient to convict than was then required.15
Yes. The provisions impose a punishment for acts such as entering or leaving the State of Missouri to avoid enrolment or draft in the military service of the United States. These acts were not punishable at the time they were committed.16 They impose additional punishment for acts that constituted high offences at the time. They also subvert the presumptions of innocence by assuming the parties are guilty and calling upon them to establish innocence only by the expurgatory oath.17
These effects match the definition of an ex post facto law, as applied when the plaintiff in error was convicted for preaching without the oath.
The test oath provisions of the Missouri constitution constitute an ex post facto law prohibited by the federal Constitution.18