Zack Cozar v. State of Mississippi, 226 So. 3d 574

In 2010 Zachary Cozart was indicted for capital murder and felonious child abuse after the death of a 21-month-old; he initially entered an Alford plea to manslaughter but later withdrew it and proceeded to jury trial in 2014.
At trial the defense submitted a manslaughter jury instruction that tracked the language of a 2013 amendment to Miss. Code § 97-3-25(2)(b) (effective July 1, 2013) creating a child-homicide subclass with an increased maximum term of 30 years.
The jury convicted Cozart of manslaughter; the trial court sentenced him to 30 years (with some time suspended and post-release supervision) under the amended statute.
The statute in effect when the offense occurred (2006) capped manslaughter at 20 years; the amendment that authorized a 30-year maximum postdated the offense.
Cozart appealed, arguing the 30-year sentence violated the Ex Post Facto Clause and that the error was plain; the Court of Appeals held Cozart waived the claim by proposing the instruction; the Mississippi Supreme Court granted certiorari.
The Supreme Court reviewed de novo whether the post–offense application of the amended statute violated the Ex Post Facto Clause and whether the failure to object was excused under plain-error review.

Issue	Plaintiff's Argument (Cozart)	Defendant's Argument (State)	Held
Whether sentencing under the 2013/2014 amended § 97-3-25 (30-year max for child homicide) violated the Ex Post Facto Clause	Cozart: Applying the increased 30-year penalty (enacted after the offense) increased punishment to his detriment and thus violated the Ex Post Facto Clause	State: Any objection was waived because Cozart's counsel submitted the manslaughter instruction tracking the amended statute; sentencing under the amendment was ameliorative compared to capital murder	The Court held the 30-year sentence violated the Ex Post Facto Clause because the harsher statute postdated the offense; application reversed and remanded for resentencing under the 2006 statute (20-year max).
Whether plain-error review applies despite failure to object at trial	Cozart: The error affected a fundamental right and was obvious; plain-error review should correct the illegal sentence	State: The instruction was a strategic, ameliorative choice and the claim is procedurally barred	The Court applied Olano plain-error standards, concluded the error was obvious, affected substantial rights and the fairness of proceedings, and exercised plain-error review to correct the ex post facto violation.

Collins v. Youngblood, 497 U.S. 37 (1990) (defines ex post facto laws)
Weaver v. Graham, 450 U.S. 24 (1981) (ex post facto and increased punishment analysis)
Olano v. United States, 507 U.S. 725 (1993) (plain-error review framework)
Barnett v. State, 725 So. 2d 797 (Miss. 1998) (waiver by failure to object to jury instructions and ameliorative-sentence analysis)
Flowers v. State, 35 So. 3d 516 (Miss. 2010) (ex post facto and defective-indictment/sentence discussion)
Johnston v. State, 618 So. 2d 90 (Miss. 1993) (sentence must follow statute in effect at time of offense)