Sentencing enhancements are policies that mandate that people who are convicted of criminalized behaviors while engaging in generally non-criminalized behaviors—such as being in a school zone—or having generally non-criminalized traits—such as having a prior conviction—receive longer and surer sentences than those who are convicted of the same criminalized behaviors without engaging in these generally non-criminal behaviors or having these traits. Some sentencing enhancements apply to all underlying crimes; this is true of the bias enhancement of Washington, DC. Other sentencing enhancements apply to all crimes of a certain category. Alabama’s firearm enhancement applies to all people convicted of drug crimes who are eligible for gun enhancements. For example, if someone is arrested while carrying ten grams of cocaine and a registered gun they will be charged with cocaine possession and given a firearm enhancement, even if they have a conceal and carry permit and thus their carrying of the firearm would have been legal absent their possession of the cocaine. A final set of sentencing enhancements apply only to a single underlying crime; one federal recidivist enhancement that applies only to the underlying crime of illegal re-entry is an example. Furthermore, some sentencing enhancements are embedded in sentencing guidelines while others are statutory. In 2005, the US Supreme Court’s Booker decision rendered guideline enhancements advisory. Nonetheless, the best available research suggests that judges still apply guideline enhancements to the abundance of defendants, saving their now available leniency for defendants without prior convictions or other defendants who they view as least culpable. Moreover, while many practitioners and policymakers have argued that the Booker decision helps to limit punitiveness and disparity in processing, others argue that this decision increases prosecutors’ power by making important factual disputes elements of the crime and depriving defendants sentencing hearings—the only hearings most were likely to have in this era of guilty pleas. Furthermore, while judges are still bound by statutory enhancements, the 2005 Shepard decision increases the kinds of evidence that judges may consider, restoring some judicial discretion even in this context. A preponderance of research suggests that sentencing enhancements play an important role in the production of the prison boom, increase racial disparities, and are disproportionately punitive toward women, leading these policies to be widely critiqued by scholars and prisoner rights groups. Moreover, while some studies suggest that sentencing enhancements have a marginal deterrent effect, other scholars note that even if this impact exists it is likely offset by the ways in which sentencing enhancements and other punitive policies increase crime by helping to produce concentrated racialized incarceration and thus destabilizing families and communities. As all of this suggests, sentencing enhancements raise a number of legal and ethical concerns; some of these concerns derive from their uneven implementation while others are implicit in their design. Changing case law has highlighted but not resolved these concerns.