This is part of the “Tools for Safe and Smart Bail System Changes” series. Read the introduction and view other posts here.

What is it?

Preventive detention is the practice of holding someone in jail before they are tried in court or convicted of a crime. Although individuals may spend some time in custody upon initial arrest, preventive detention involves continued detention of individuals based on the perceived risk they pose to society or the likelihood that they will not show up in court.

Preventive detention was primarily intended for ensuring a defendant’s appearance in court; however, in United States v. Salerno, the U.S. Supreme Court expanded the purpose of preventive detention to include protecting public safety as a legitimate justification. Since then, jurisdictions have worked to implement preventive detention as a part of their bail system. The District of Columbia pioneered preventive detention measures in 1970, subsequently inspiring many states to amend their constitutions to allow for some form of preventive detention. This trend continued into recent years, with New Jersey expanding preventive detention-eligible offenses in their constitution in 2014, followed by New Mexico in 2016 and Arizona in 2018. Most recently, Delaware and Indiana embraced this approach.

Each state has its own legal framework and criteria for determining when preventive detention is appropriate, and it varies widely from jurisdiction to jurisdiction. While some states are directed by their constitution, others are guided by state legislation or court rules. To maintain a delicate balance between safeguarding individual rights and preserving public safety, many states have enshrined clear limitations within their law. These limitations steer the application of detention as an exception rather than a commonplace practice.

Legal safeguards restrict the use of preventive detention by establishing clear criteria and boundaries for its application. Similar to eligible offenses, these protections can be outlined within constitutional provisions, state statutes or court rules and serve to protect the fundamental principle of the presumption of innocence until proven guilty. Moreover, legal safeguards frequently emphasize the importance of due process, including the right to a fair and timely hearing to challenge detention, as well as the consideration of less restrictive alternatives to custody, such as supervised release or electronic monitoring. There is a belief that the Salerno decision necessitates some of these protections, but there are no established criteria or tests for this analysis. Safeguards include the following:

(Download table.)

What concerns does this address?

Preventive detention allows authorities to proactively manage potential risks posed by individuals who may possess violent tendencies or extremist ideologies or have expressed threats of harm to others. This is particularly important in cases where there is credible evidence or intelligence indicating that the individual poses a serious risk to society or to a particular victim. It can provide an opportunity to assess and address these risks before they escalate into criminal actions.

Preventive detention can also help law enforcement and legal authorities prevent defendants from fleeing the jurisdiction. If a defendant continues to be incarcerated, they remain available for legal proceedings. This is particularly relevant in situations involving serious offenses where someone may be trying to evade a lengthy prison sentence or cases where the individual has a history of evading authorities.

A court is prohibited from imposing excessive bail, but the lack of a clear definition for “excessive” has led to widespread use of high cash bail to preventively detain defendants in many states. This affects those with limited financial resources—often traditionally marginalized communities—the most. Consequently, individuals who pose no substantial flight risk or threat to public safety may languish in custody solely because they cannot afford their bail. At the same time, dangerous individuals with financial means can pay for their release. The use of preventive detention can assure that custody is applied more effectively and fairly.

In states where cash bail has been either formally abolished or effectively eliminated, the need for preventive detention becomes a critical consideration. With the high cash bail option effectively removed as a de facto form of preventive detention, courts may find themselves with limited alternatives for handling high-lethality or flight-risk defendants, potentially exposing communities to heightened risks. This is particularly concerning in communities lacking comprehensive safety measures like pretrial services, electronic monitoring or pretrial support.

Is it effective?

The effectiveness of preventive detention is a subject of ongoing debate and varies depending on its defined goals and measurement. Preventive detention effectively mitigates flight and safety risks by confining individuals to a jail cell until their case is resolved. However, it can be costly if wrongly applied due to erroneous predictions of future behavior. Thus, the overall effectiveness of preventive detention primarily hinges on the court’s ability to make accurate forecasts of an individual’s likelihood to flee or cause harm if released.

Concerningly, studies show that judges wrongfully release about half of the highest-risk defendants. Risk assessments only have an accuracy rate of approximately 55 to 70 percent. There is no crystal ball to see into the future behavior of individuals arrested for crimes. Achieving absolute safety is instead an elusive goal, as attaining it would necessitate intrusive measures on individual liberties that would impact a significantly larger number of people who pose no serious harm, compared to the relatively small amount who might.

The accuracy of predicting risk is further challenged because the individuals to be studied often remain detained pretrial, eliminating their chance to reoffend or miss court. Many states also do not compile or disclose rearrest and failure-to-appear rates for pretrial defendants, making it hard to determine when pretrial detention decisions are correct or make meaningful comparisons among states with different preventive detention laws.

States have taken varied approaches to delineate which types of offenses qualify for pretrial detention, most restricting the application.

(Download table.)

The prevailing standard of proof used to determine if a defendant’s offense is eligible for preventive detention is the high standard of “proof evident, presumption great.” Research shows persistent violent offenders, characterized by prior criminal behavior, are more likely to reoffend. Therefore, focusing on high-level violent offenses with evident proof of guilt could likely enhance predictive accuracy, especially if it is used only when a crime is committed while a person is already out on bail. Further, the use of risk assessments in addition to employing more thorough, comprehensive detention hearings could also improve accuracy. And requiring detention as a “last resort” to address flight and safety risk can limit unnecessary use.

It could be argued, though, that effectiveness is actually measured by whether preventive detention more accurately keeps high-risk offenders in jail than by the setting of cash bail. When bail decisions focus on whether or not to detain rather than on price tags for release, effectiveness seems evident.

What challenges or concerns does it present?

Preventive detention can be controversial due to its potential to infringe upon an individual’s presumption of innocence and right to liberty before being proven guilty. However, proponents argue that it is necessary to balance individual rights with the safety of the broader community, especially in cases where there is strong evidence of a potential threat. This balance is a complex challenge that requires careful consideration and adherence to legal safeguards.

Detaining individuals pretrial can have significant social and economic consequences for their families and communities. It can lead to job loss, disruption of family life and other hardships. Improper use of pretrial detention may lead to the unjustified jailing of low-risk or innocent individuals, inflicting potentially irreversible harm upon them. Research indicates that such practices can subsequently contribute to increased rates of reoffending, thereby undermining future public safety.

Maintaining a pretrial detention system can also be expensive, as it involves the cost of housing and caring for detainees. This can strain resources that might be otherwise allocated to other critical aspects of the criminal justice system, such as providing behavioral support within the jails, meeting staffing needs or implementing additional crime prevention measures. Research has consistently demonstrated that alternatives to incarceration can yield substantial cost savings, underscoring the imperative to ensure that preventive detention measures are employed judiciously—and only when absolutely essential.

Preventive detention policies have been criticized for disproportionately affecting marginalized communities and low-income individuals. This also pertains to high cash bail and its disproportionate impact on certain segments of the population. The concern is that marginalized communities are detained more often because of bias within risk assessments or unconscious bias within judges themselves.


Preventive detention can be effective in ensuring court appearances and protecting public safety in certain cases, but it also raises concerns about the presumption of innocence, social impacts, costs and potential disparities in its application. Thus, it should be an option of last resort, reserved for cases where there is evident proof of someone’s guilt and compelling evidence of a defendant’s flight risk or a demonstrable threat to public safety. It should be used sparingly and only under strict legal frameworks, with oversight from the judiciary and clear criteria for when it can be invoked. The potential for abuse and violation of human rights necessitates a cautious and transparent approach to its implementation.

As states move toward the elimination of cash bail and a presumption of pretrial release framework, the use of preventive detention becomes an essential tool for courts and prosecutors to use when a defendant poses a risk of flight or safety. Abandoning the widespread use of cash bail for detaining high-risk individuals should not be taken lightly. There must be safety and accountability measures in place to ensure that a fairer system for the accused does not come at the expense of community safety.