Plea Bargains and Wrongful Convictions: Northwestern Professor's Findings
From depictions in the media, it’s easy to assume the criminal justice system is centered in courtrooms.
In reality, less than 3% of federal criminal cases were settled in trial in fiscal year 2022. Rather, the vast majority were settled in plea deals where defendants pleaded guilty in exchange for lighter sentences.
Northwestern professor and applied macroeconomist Alexander Lundberg evaluated how this practice impacts wrongful convictions in a paper recently published in Economic Inquiry.
Using game-theoretic models, economists have analyzed how plea bargaining affects sentencing. Some argue that plea bargaining expands a defendant’s choice set and thus can only benefit defendants.
Others have suggested that — because innocent defendants expect to do better at trial than guilty defendants — plea deals could predict whether a defendant is guilty or innocent based on their willingness to take various deals.
“A lot of these models I found really engaging,” Lundberg said. “But at the same time, when I speak to people involved in the justice system, I’ve found the conclusions ultimately unconvincing.”
Instead, Lundberg found that relaxing the assumptions built into previous models challenged many of these conclusions. Lundberg’s adjusted model found that plea bargains lead to wrongful convictions, a result in line with anecdotal evidence.
“If you’re really worried about what could happen going to trial — which is also a pain and a lot of effort — it might seem like it’s a no-brainer,” he said. “You kind of have to accept this deal whether you actually are guilty or not.”
In Lundberg’s model, a partial ban on plea bargaining prevents prosecutors from offering “steep discounts attractive to both guilty and innocent defendants” while allowing them to continue making small discounts that only guilty defendants would find attractive. The model further found that relaxing plea bargain restrictions leads to an increase in wrongful convictions.
The paper also explains how the police control the defendant’s perceived probability of guilt based on the initial evidence gathered. Based on this finding, Lundberg presented an alternative solution to partial plea bans: reallocating a portion of the prosecutorial budget to the police. This would restrict prosecutors to focusing on the strongest cases and allocate resources to the police to better identify guilty defendants.
Lundberg said that, while policy change stemming from individual research is unlikely, researchers hope that their combined efforts can influence tangible change. He referenced the growing intersection of policy and economics including law schools offering economics courses and amicus briefs that reference economic concepts.
“You hope that a collective voice might emerge from the literature,” he said.
As plea deal research has expanded, the Supreme Court has begun to protect the rights of defendants who plead guilty or are considering a plea bargain.
While theoretical models can illustrate how rational actors should behave, real-world data surrounding wrongful convictions is severely limited. Some economists have relied on simulation models or random assignment to stricter judges in attempts to measure how the risk of trial impacts defendant decision making.
Still, there are limited data-driven studies on the impacts of plea bargaining. As data sets expand — such as through The Innocence Project’s 250 overturned convictions — Lundberg plans to further investigate this issue using quantitative analysis.
“We finally have more data on wrongful convictions that have been overturned,” Lundberg said. “As those datasets develop further and further, I think the opportunity for a more data-driven study to follow this kind of work is growing.”