Stop, Frisk, and Save Lives II

I ended the earlier post with this:

If you want less crime, you have to lock up criminals. In order to lock up criminals, you have to identify them.

There’s new proof of the wisdom of “stop and frisk”:

[A] reduction in stop and frisks by the Chicago Police Department that began at the very end of 2015 was responsible for the homicide spike starting immediately thereafter. Good reasons exist for believing that the decline in stop and frisks caused the spike. Simple visual observation of the data suggests a cause-and-effect change. In the chart below, we depict the (seasonally unadjusted) monthly number of stop and frisks (in blue) and the monthly number of homicides (in gold). The vertical line is placed at November 2015—the break point in the homicide data. This is precisely when stop and frisks declined in Chicago.


Detailed regression analysis of the homicide (and related shooting) data strongly supports what visual observation suggests. Using monthly data from 2012 through 2016, we are able to control for such factors as temperature, homicides in other parts of Illinois, 9-1-1 calls (as a measure of police-citizen cooperation), and arrests for various types of crimes. Even controlling for these factors, our equations indicate that the steep decline in stop and frisks was strongly linked, at high levels of statistical significance, to the sharp increase in homicides (and other shooting crimes) in 2016. [Paul Cassell, “The 2016 Chicago Homicide Spike – Explained“, The Volokh Conspiracy, March 26, 2018]

You can’t drum me out of the libertarian camp. I left it voluntarily several years ago.

2 thoughts on “Stop, Frisk, and Save Lives II

  1. An example somewhat related to “Stop and Frisk”: Some years ago, in Arizona, a state patrolman was cruising on the freeway south of Tucson. He observed a pickup truck heading toward the Mexican border. The truck had a license plate indicating it had been licensed in northern Arizona, near Flagstaff. He knew the truck was of a type highly valued in Mexico. He observed that the driver appeared to be Hispanic. He suspected that the truck was stolen. He stopped the vehicle and, sure enough, the driver was either a Mexican or a Mexican-American (I can’t remember which) and the truck had been stolen. He arrested the driver. In court, the case was dismissed on the grounds that the patrolman had illegally profiled the driver and otherwise had no probable cause to stop the truck.


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