Risk assessment algorithms--statistical formulas that predict the likelihood a person will commit crime in the future--are used across the country to help make life-altering decisions in the criminal process, including setting bail, determining sentences, selecting probation conditions, and deciding parole. (1) Yet many of these instruments are "blackbox" tools. The algorithms they use are secret, both to the sentencing authorities who rely on them and to the offender whose life is affected. The opaque nature of these tools raises numerous legal and ethical concerns. In this paper we argue that risk assessment algorithms obfuscate how certain factors, usually considered mitigating by sentencing authorities, can lead to higher risk scores and thus inappropriately inflate sentences. We illustrate this phenomenon through one of its most dramatic manifestations: The role of age in risk assessment algorithms. (2)
When considered as a factor at sentencing, youthfulness can be a double-edged sword--it can both enhance risk and diminish blameworthiness. If either risk or culpability is the sole issue at sentencing, this potential conflict is avoided. But when, as is often the case, both risk and culpability are considered relevant to the sentence, the aggravating effect of youth should presumably be offset or perhaps eliminated entirely by its mitigating impact. If judges and parole authorities are fully informed of the conflicting roles youth plays in a particular case, they can engage in this balancing act as appropriate. However, when information about risk comes from a black-box algorithm, they are unlikely to know the extent to which the risk evaluation is influenced by the defendant's youthfulness. In such cases, their decisions about pretrial detention, sentence, or release may unknowingly give youth too much weight as an aggravator.
Further, even if the black box is opened and the risk assessment algorithm is made publicly available, the risk score may not be conveyed in a fully transparent manner. For instance, while judges may be told that an offender's youth is a risk factor, the relative weight of age in the overall score may not be fully explained or understood at the time of decision-making. (3) Unless the judge makes specific inquiries, she will not be informed of the variables that contributed most heavily to a particular defendant's risk score.
This decisional blindness is especially pernicious in light of the impression created by the labels associated with these instruments--"high risk" or "high risk of violence." Such labels not only convey information about the potential for recidivism. They are also suggestive of bad character, or at least a history of bad decision-making. In other words, these labels convey condemnation. Such condemnation might be appropriate for an individual who has earned the "high-risk" classification by committing multiple violent or ruthless acts. But it is not warranted for an individual who has earned that label largely because of his or her youth.
To ensure sentencers take this double-edged sword problem into account, risk assessment algorithms should be transparent about the factors that most heavily influence the score. Only in that way can courts and legislators engage in an explicit discussion about whether, and to what extent, young age should be considered a mitigator or an aggravator in fashioning criminal punishment.
In Part I, we discuss the tensions youthfulness generates in the post-conviction setting by introducing the double-edge sword phenomenon and the jurisprudence that has developed around it. In Part II, we present empirical evidence that shows how influential age is in the widely-used COMPAS Violent Recidivism Risk Score (VRRS) and in other common risk assessment tools. Specifically, we conduct a partial decomposition of the VRRS to show that age alone can explain almost 60% of its variation, substantially more than the contributions of criminal history, gender or race. Similar patterns are documented in other common risk scores. In Part III, we discuss how obfuscation of age's impact on the risk score improperly undermines consideration of youthfulness as a mitigating factor. We also discuss how the points we make about the role of youth might apply to a number of other factors that are often used in structured risk assessments, including mental illness, substance abuse, and socio-economic factors. While our discussion centers on sentencing, the main argument is generally relevant to a broad range of settings in which risk assessments influence criminal justice outcomes.
THE ROLE OF YOUTH IN SENTENCING
Reliance on youth at sentencing can raise at least three issues that resonate with constitutional prohibitions. The first is whether basing a sentence in whole or in part on youth raises an equal protection claim. Some have argued that age classifications, like those based on gender and race, should be subject to heightened scrutiny. (4) The second arises from the notion, recently solidified by the Supreme Court into constitutional doctrine where race is involved, that punishment should not be based on status. (5) Although both of these issues require careful thought, neither is addressed here.
The focus of this article will instead be on a third issue: how youth is used in conflicting ways at sentencing, and the reasons--arguably also of constitutional magnitude--that such use is questionable. This focus requires an examination of the "double-edged sword" dilemma, and the ways in which courts have dealt with it. While the issues discussed in this article relate to both the juvenile justice system and the adult criminal justice system, we focus our analysis exclusively on the adult system and adult risk assessment tools. Thus, when we refer to youths, we are referring only to those in their late teens and early twenties who are initially prosecuted in adult court, and to those under the age of eighteen who have been transferred to the adult system.
Youth as a Double-Edged Sword
In the American legal system, youth is often a strong basis for leniency in punishment. The most obvious evidence of this stance is the fact that every state has established a juvenile court system that diverts young offenders away from the harshness of adult criminal justice. (6) In adult sentencing regimes as well, youth is often treated as a mitigator, which in some situations is even constitutionally required. In Roper v. Simmons, (7) the Supreme Court held that the imposition of the death penalty on juvenile offenders who have been transferred to adult court violates the Eighth Amendment. Seven years later, in Miller v. Alabama, (8) it concluded that the Eighth Amendment also bars mandatory life without parole sentences for juvenile offenders. In both decisions, the Court emphasized the inverse relationship between adolescence and culpability. As Justice Kagan put it in Miller, "[bjecause juveniles have diminished culpability and greater prospects for reform, ... 'they are less deserving of the most severe punishments." (9) Subsequent developments have made clear that the thousands of minors who are transferred out of the juvenile system and subject to sentences short of the death penalty and life without parole are also explicitly encompassed by the mitigation rationale developed in the Supreme Court's decisions. (10)
The Supreme Court's decisions draw a bright line at the age of eighteen. But the rationale of Roper and its progeny clearly does not evaporate at that age. Influenced by those cases, some jurisdictions have recently expanded juvenile court jurisdiction beyond eighteen. (11) More importantly, well before Roper, most capital sentencing statutes treated young (post-adolescent) adulthood as a mitigating factor when deciding whether the death penalty is appropriate. (12) A similar practice has long existed in non-capital sentencing practice. For instance, the Federal Sentencing Guidelines state that "age (including youth) may be relevant in determining whether a departure is warranted, if considerations based on age, individually or in combination with other offender characteristics, are present to an unusual degree and distinguish the case from the typical cases covered by the guidelines." (13) State regimes are often even more explicit about making post-adolescent youth a mitigating consideration at sentencing. (14)
At the same time, intuition suggests--and research indicates (15)--that youthfulness can also be an aggravating factor. The Supreme Court has often observed that juveniles are less "deferrable" than adults. (16) Although that language is meant to support the Court's conclusion that youth is a mitigating factor, it also recognizes that young people tend to be more impulsive, less risk averse, more easily influenced by peers, and less constrained by "stakes in life"--all of which tend to increase the likelihood that young people will engage in criminal activity. (17) If the goal is to prevent crime via incapacitation, one might argue that it is logical to incarcerate youths through the years of peak criminal activity.
As a legal matter, these facts give rise to the familiar "double-edged sword" problem. (18) Depending upon the purpose of punishment at issue, the same factor can be seen as either mitigating or aggravating. Because they diminish culpability and control, factors like youth and mental disability may well be mitigating from a retributive or deterrence perspective. From an incapacitative perspective, however, they may be aggravating factors, because they enhance risk.
Sentencing practices reflect this tension. In a meta-analysis of approximately 60 studies examining the effect of age on sentences, Jaejong Wu and Cassia Spohn found that 40% of the studies reported a positive relationship between these two variables (i.e., older offenders received longer sentences), 57% reported a negative relationship, and 3%...