Algorithms should have made courts more fair. What went wrong?

Enlarge / The courts have become another frontline in the battle against climate change. (credit: Patrick Feller / Flickr)

Kentucky lawmakers thought requiring that judges consult an algorithm when deciding whether to hold a defendant in jail before trial would make the state's justice system cheaper and fairer by setting more people free. That's not how it turned out.

Before the 2011 law took effect, there was little difference between the proportion of black and white defendants granted release to await trial at home without cash bail. After being mandated to consider a score predicting the risk a person would reoffend or skip court, the state's judges began offering no-bail release to white defendants much more often than to black defendants. The proportion of black defendants granted release without bail increased only slightly, to a little over 25%. The rate for white defendants jumped to more than 35%. Kentucky has changed its algorithm twice since 2011, but available data shows the gap remained roughly constant through early 2016.

The Kentucky experience, detailed in a study published earlier this year, is timely. Many states and counties now calculate "risk scores" for criminal defendants that estimate the chance a person will reoffend before trial or skip court; some use similar tools in sentencing. They are supposed to help judges make fairer decisions and cut the number of people in jail or prison, sometimes as part of eliminating cash bail. Since 2017, Kentucky has released some defendants scored as low-risk based purely on an algorithm's say-so, without a judge being involved.

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