The Unintended Impact of Pretrial Detention on Case Outcomes: Evidence from NYC Arraignments

Emily Leslie and Nolan G. Pope

On any given day in the United States, over 400,000 individuals are in jail awaiting trial (Wagner and Sakala 2014) at a cost of 9 billion dollars per year (Holder 2011). In addition, the combined population of local jails grew by 20% between 2000 and 2014, with 99% of the growth due to the expanded pretrial jail population (Wagner 2015). The large majority of these detainees are prevented from returning home while their cases are adjudicated because they do not have access to the financial resources to post bail: about 38% of felony defendants have bail set, and nearly 9 out of 10 of these failed to post bail (Reaves 2013). Of those held on bail, an estimated 81 percent have bail set at less than 5,000 dollars and 44 percent have bail set at less than 1,000 dollars (Phillips 2012).

Given that the high levels of pretrial detention are driven by failure to post bail, even at low levels of bail, low-income individuals are particularly vulnerable to the adverse effects of pretrial detention. Detainees may miss work, and therefore forego income or even lose employment, and they are unable to attend to family responsibilities or access their social support network. Detained individuals also face stronger incentives to plead guilty. For defendants charged with minor offenses, pleading guilty often results in immediate release. Because time spent in jail awaiting trial is counted against sentence length, the cost of pleading guilty is lower for defendants facing more serious charges as well because they are effectively paying part of the price of conviction in advance.

In our paper, we instrument for pretrial detention status using judge-specific propensities to detain, allowing us to isolate the causal effect of detention on conviction and other case outcomes. We use data from nearly a million felony and misdemeanor criminal cases in New York City from 2009 to 2013, including information linking defendants with arraignment judges. After confirming empirically that judges are randomly assigned, we estimate how an increase in the probability of pretrial detention, driven solely by the arraignment judge, affects the probability of pleading guilty, being convicted, and length of sentence.

Our results show that pretrial detention substantially increases the probability that a defendant will be convicted. The increase in conviction rates is driven by detainees accepting plea deals more frequently. We also find some evidence that detention increases minimum sentence length. Detention affects case outcomes for defendants in both misdemeanor and felony cases. Our estimates are robust to adding a variety of demographic, criminal history, and most serious offense charge controls. Relaxing the monotonicity assumption associated with standard IV yields similar results. Although effects do not vary noticeably across racial and ethnic lines, minorities are overrepresented in the sample and are therefore disproportionately affected by pretrial detention.

The adverse effects of detention on case outcomes could operate through a variety of mechanisms. Conventional wisdom among those employed in the criminal justice system is that detainees plead guilty to return home quickly. Large effects for people charged with minor crimes support this hypothesis, because many of these individuals have access to plea deals that do not require any additional time incarcerated. Defendants with dependents may be especially prone to pleading guilty quickly so they can be with their children. We find evidence that women are more likely than men to plead guilty when they are facing less serious charges; there is no difference in effects for men and women facing more serious charges. However, even individuals who will almost certainly spend more time behind bars after pleading guilty tend to do so more often if detained. This group has already served part of their time in advance, making accepting a plea deal relatively less costly.


Emily Leslie is a doctoral candidate in the Tippie College of Business at the University of Iowa. Nolan Pope is a doctoral candidate in the Department of Economics at the University of Chicago.