*453 OPINION
Defendant Martino Moore, a four-time convicted felon, possessed a firearm one night in 2007. That event carried with it serious ramifications. It meant as an Armed Career Criminal he was subject to a mandatory minimum penalty of 180 months’ imprisonment. Moore argues on appeal thаt the imposition of this mandatory minimum sentence, as applied to him, violates the Eighth Amendment. We disagree and thus affirm.
I.
On March 9, 2007, Memphis police responded to a call about an assault. At the scene, police interviewed Precious Jackson. She claimed that her bоyfriend Moore beat her, pointed a firearm at her, and threatened to kill her. Two witnesses informed the officers that they had seen Moore beat Jackson and that he had a firearm. But neither witness saw Moore point the gun at Jackson. The police located Mоore near the scene with the firearm, an AMT .22 caliber semi-automatic pistol, still in his possession. They arrested him without incident.
Moore explained that the fight erupted when Jackson took his cell phone. He claimed that he took the gun away from her during the fight, but he denied hitting or pointing the gun at her.
On February 15, 2008, a federal grand jury in the Western District of Tennessee indicted Moore for being a felon in possession of a firearm in violation of 18 U.S.C. § 922(g). Moore’s attorney requested that Moore undergo a competency evaluation. On June 3, 2008, doctors at the Fеderal Medical Center in Kentucky diagnosed Moore with mild mental retardation 1 but concluded that he was nevertheless competent to stand trial. The doctors found that Moore had a factual and rational understanding of the proceedings against him and retained the ability to consult with his attorney. Moore did not challenge these findings and later pleaded guilty under a written plea agreement.
Moore’s Presentence Report listed two violent felonies and two serious drug felonies: (1) a 1994 conviction for aggravated burglary; (2) a 1997 conviction for criminal attempt to commit aggravated burglary; (3) a 2000 conviction for possession of crack cocaine with intent to manufacture, deliver, or sell; and (4) another 2000 conviction for possession of crack cocaine with intent to manufacture, deliver, or sell. PSR, ¶¶ 25, 26, 28, 30. As а result, he qualified as an “Armed Career Criminal” under U.S.S.G. § 4B1.4(b)(3)(A) and 18 U.S.C. § 924(e). He also received a four-level enhancement for being a felon in possession of a firearm in connection with another felony offense — aggravated assault. His guideline range was 188-235 months, with a statutory minimum of 180 months under § 924(e).
Moore objected to the four-level enhancement at the sentencing hearing. Because the United States could not locate Ms. Jackson to confirm whether Moore had in fact pointed the gun at her or hit her with the gun, it agreed that Moore’s offense level shоuld be reduced, with a new corresponding guideline range of 151-188 months. But under § 924(e), the mandatory minimum sentence still stood at 180 months. Moore’s attorney told the court that he knew of no grounds permitting the court to go below the 180-month minimum. The district court judge remarked that, if he had the authority to do sо, he *454 would consider imposing a sentence below the statutory minimum due to the circumstances of the offense and Moore’s mental deficiencies. R. 49 at 32. He nevertheless acknowledged that he did not possess that authority and proceeded to sentence Moore to 180 months’ imprisonment. Moore filed a timely appeal.
II.
Moore argues that his mandated minimum sentence of fifteen years’ imprisonment violates the Eighth Amendment’s ban on cruel and unusual punishment. At the heart of his argument is the belief that a unique mitigating factor — his reduced culpability rеsulting from mental retardation — transforms an otherwise constitutional sentence into an unconstitutional one. In
United States v. Tucker,
we held that “[ijmposing a mandatory minimum sentence on a defendant with limited mental capabilities does not violate the Eighth Amendment ban against cruel and unusual punishment.”
A.
As an initial matter, “[a] constitutional challenge to a sentence is a question of law and reviewed
de novo.” United States v. Jones,
B.
The Eighth Amendment provides: “Excessive bail shall not be required, nor excessive fines imposed, nor cruel and unusual punishments inflicted.” U.S. Const, amend. VIII. Moore is correct that the Supreme Court has interpreted the Eighth Amendment to contain a “narrow proportionality principle.”
Harmelin v. Michigan,
While we have traditionally not engaged in proportionality review when the sentence is a term of years,
see United States v. Thomas,
Contrary to Moore’s claim, this sentence
did
account for his mental retardation. Even though the guidelines authorized a sentence up to 188 months, the statute imposed no such cap.
See Custis v. United States,
The acknowledgment in
Atkins v. Virginia
that mentally retarded defendants are “categorically” less culpable than average criminals likewise fails to render this statutory penalty unconstitutional.
Further,
Atkins
did not offer a blanket exemption from ordinary punishmеnts to the mentally handicapped or cast aside mandatory minimum sentences. Rather, the Court recognized that mentally retarded defendants face a special risk of wrongful execution because they may have difficulties assisting their counsel, they are
*456
often poor witnesses, and their demeanor may convey an “unwarranted impression of lack of remorse for their crimes.”
Atkins,
This does not mean that a defendant’s culpability is irrelevant in non-capital cases. In considering whether a punishment is grossly disproportionate, culpability plays a role.
Solem,
Fifteen years is by any measure a considerable amount of time. But while “[s]evere, mandatory penalties may be cruel, ... they are not unusual in the constitutional sense, having been employed in various forms throughout our Nation’s history.”
Harmelin,
Because a “threshold comparison” of the gravity of Moore’s offense and the severity of his sentence does not reveal an inference of gross disproportionality, we need not engage in the second step of the proportionality analysis by comparing his sentence with those of offenders in this and other jurisdictions.
Harmelin,
C.
Moore’s suggestion that his sentence is rendered unconstitutional by the
*457
decision in
Graham v. Florida,
— U.S. -,
To begin, the penalty was unusually grave. Along with death sentences, sentences of life without the possibility of parole are unique in their severity.
Id.
at 2027 (citing
Harmelin,
The unique concerns that prompted the Supreme Court to closely scrutinize the sentence in Graham are not present here. Most significantly, Moore’s fifteen-year sentence is vastly lighter. Unlike a juvenile non-homicide offender sentenced to life without parole, Moore will likely see the outside of a prison. He has hope for eventual release in a way that Graham did not. Also, the rehabilitation opportunities not available to juvenile nоn-homicide offenders sentenced to life without parole will be available to Moore. Moore can take advantage of the rehabilitative services of which the Court spoke in Graham. Id. at 2030.
Further, Moore is an adult. The
Graham
Court noted that real differences exist between juvenile and adult minds.
Id.
at 2026. It recоgnized that juveniles possess the ability to change, with their actions less likely revealing “evidence of ‘irretrievably depraved character’ than ... the actions of adults.”
Id.
(citing
Roper v. Simmons,
Thus, the Supreme Court’s concerns in Graham are simply not present here.
III.
Moore’s Eighth Amendment challenge to his sentence fails even under a de novo standard of review. We therefore AFFIRM the sentence of the district court.
Notes
. Like the briefs and doctors, we use the term "mental retardation” in order to be medically precise. We mean no disrespect by using the term.
