The Deterrent Effect of DNA Databases

The killing of George Floyd has prompted a great deal of debate over whether the US should reduce the size of its police departments. The research literature suggests that the presence of police officers does reduce crime, though they're expensive and as is increasingly recognised, impose substantial harms on the populations they are meant to be protecting, especially communities of colour.

 So maybe we ought to shift our focus to effective but unconventional approaches to crime prevention, approaches that don't require police or prisons and the human toll they bring with them.

 Today’s guest, Jennifer Doleac — Associate Professor of Economics at Texas A&M University, and Director of the Justice Tech Lab — is an expert on empirical research into policing, law and incarceration. In this extensive interview, she highlights three alternative ways to effectively prevent crime: better street lighting, cognitive behavioral therapy, and lead reduction.

One of Jennifer’s papers used switches into and out of daylight saving time as a 'natural experiment' to measure the effect of light levels on crime. One day the sun sets at 5pm; the next day it sets at 6pm. When that evening hour is dark instead of light, robberies during it roughly double.

Links to sources for the claims in these show notes, other resources to learn more, and a full transcript.

The idea here is that if you try to rob someone in broad daylight, they might see you coming, and witnesses might later be able to identify you. You're just more likely to get caught.

You might think: "Well, people will just commit crime in the morning instead". But it looks like criminals aren’t early risers, and that doesn’t happen.

On her unusually rigorous podcast Probable Causation, Jennifer spoke to one of the authors of a related study, in which very bright streetlights were randomly added to some public housing complexes but not others. They found the lights reduced outdoor night-time crime by 36%, at little cost.

The next best thing to sun-light is human-light, so just installing more streetlights might be one of the easiest ways to cut crime, without having to hassle or punish anyone.

The second approach is cognitive behavioral therapy (CBT), in which you're taught to slow down your decision-making, and think through your assumptions before acting.

There was a randomised controlled trial done in schools, as well as juvenile detention facilities in Chicago, where the kids assigned to get CBT were followed over time and compared with those who were not assigned to receive CBT. They found the CBT course reduced rearrest rates by a third, and lowered the likelihood of a child returning to a juvenile detention facility by 20%.

Jennifer says that the program isn’t that expensive, and the benefits are massive. Everyone would probably benefit from being able to talk through their problems but the gains are especially large for people who've grown up with the trauma of violence in their lives.

Finally, Jennifer thinks that lead reduction might be the best buy of all in crime prevention…

Blog post truncated due to length limits. Finish reading the full post here.

In today’s conversation, Rob and Jennifer also cover, among many other things:

• Misconduct, hiring practices and accountability among US police
• Procedural justice training
• Overrated policy ideas
• Policies to try to reduce racial discrimination
• The effects of DNA databases
• Diversity in economics
• The quality of social science research

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Producer: Keiran Harris.
 Audio mastering: Ben Cordell.
 Transcriptions: Zakee Ulhaq.