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JULY 1994

Article 15 - Prohibition of Ex Post Facto Laws

The U.S. Constitution forbids both the federal 
government and states from enacting ex post facto 
laws.  Art. I,   9 of the Constitution, addressing 
the duties of the U.S. Congress, states that "No . . 
. ex post facto Law shall be passed."  Art. I.   10 
provides that "No State shall . . . pass any . . . 
ex post facto Law."  An ex post facto law would 
retroactively make unlawful conduct that was lawful 
when it was committed or would increase criminal 
penalties retroactively.  The prohibition on ex post 
facto laws applies to Congress and the states.  See 
Calder v. Bull, 3 U.S. (3 Dall.) 386 (1789); Dobbert 
v. Florida, 432 U.S. 282, 292-94 (1977); Collins v. 
Youngblood, 497 U.S. 37, 110 S.Ct. 2715, 2719 

These constitutional provisions preclude the 
retroactive application of a penal statute where the 
statute would, after the fact, make criminally 
punishable an act that was legal when done.  The 
prohibition against ex post facto legislation also 
forbids the state from imposing a higher penalty for 
a criminal act than was available at the time the 
crime occurred.  This prohibition has been relied on 
to invalidate application of a statutory change that 
would have made  mandatory a maximum penalty that 
was not required at the time the crime was 
committed, Lindsey v. Washington, 301 U.S. 397 
(1937), or that would have imposed a higher 
"guideline" sentence for the underlying criminal 
conduct than was in force at the time the crime was 
committed, Miller v. Florida, 482 U.S. 423 (1987), 
or that would eliminate prison credit for good 
behavior, Weaver v. Graham, 450 U.S. 24 (1981).  The 
U.S. Supreme Court also has invalidated the 
retroactive application of certain procedural 
changes, such as a law requiring fewer jurors in a 
state criminal trial, under the ex post facto 
clause.  Thompson v. Utah, 170 U.S. 343 (1898).  The 
ex post facto clause bars the application of an 
extended statute of limitations after the period 
under the original statute of limitations had run.

At the same time, however, other matters may be 
subject to retroactive amendment.  Changes in trial 
or post-trial procedures or in the rules governing 
admission of evidence, for example, may apply to 
prosecutions for offenses that occur before the 
statutory or rule changes; retroactive application 
does not trigger ex post facto concerns.  E.g., 
Collins v. Youngblood, supra (change in procedure 
allowing reformation of an improper jury verdict); 
Splawn v. California, 431 U.S. 595 (1977) (change in 
jury instructions); Thompson v. Missouri, 171 U.S. 
380 (1898) (change in evidentiary rules).  

While the Constitution thus prohibits imposition of 
punishment upon an offender that was statutorily 
unavailable at the time he committed the offense, 
the Constitution does not require that offenders 
benefit from less onerous laws passed after the 
commission of the crime.  As the Supreme Court 
explained, "for a law to be ex post facto it must be 
more onerous than the prior law."  Dobbert v. 
Florida, 432 U.S. 282, 294 (1977).  In other words, 
new laws that are less onerous do not raise ex post 
facto concerns.  State and federal courts permit the 
retroactive application of more lenient statutes but 
do not require it.  For example, when the Federal 
Sentencing Commission lowers a sentencing range, 
that change is not automatically applicable to those 
defendants previously sentenced under the earlier, 
higher range.  The sentencing court may reduce the 
sentence "if such a reduction is consistent with 
applicable policy statements issued by the 
Sentencing Commission."  18 U.S.C.   3582(c)(2).

U.S. Reservation.  Because of the contrast between 
Article 15, paragraph 1, clause 3 -- which requires 
post-offense reductions in penalty to accrue to the 
offender's benefit -- and U.S. laws, which do not 
necessarily give an offender the benefit of 
subsequent reductions of penalty, the United States 
conditioned its ratification of the Covenant upon 
the following reservation to paragraph 1 of Article 

As U.S. law generally applies to an offender the 
penalty in force at      the time the offense was 
committed, the United States does not      adhere to 
the third clause of paragraph 1 of Article 15.
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