PULLMAN, Wash. — Researchers at Washington State University say the legalization of marijuana in Washington and Colorado has not hurt police effectiveness, but instead has improved clearance rates for certain crimes.
The researchers describe clearance rates as “the number of cases solved, typically by the arrest of a suspect.”
According to the study, “clearance rates were falling for violent and property crimes in the two states before they authorized retail sales of marijuana late in 2012. The rates then improved significantly in Colorado and Washington while remaining essentially unchanged in the rest of the nation, according to the researchers’ analysis of monthly FBI data from 2010 through 2015.”
As a whole, the study found that after legalization:
Arrest rates for marijuana possession dropped considerably. Following legalization in 2012, they dropped nearly 50 percent in Colorado and more than 50 percent in Washington.
Violent crime clearance rates shifted upward.
Burglary and motor vehicle theft clearance rates “increased dramatically.”
Overall property crime clearance rates jumped sharply and reversed a downward trend in Colorado.
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“Our results show that legalization did not have a negative impact on clearance rates in Washington or Colorado,” said David Makin, assistant professor in WSU’s Department of Criminal Justice and Criminology “In fact, for specific crimes it showed a demonstrated, significant improvement on those clearance rates, specifically within the realm of property crime.”
Malkin said the improvement in burglary clearance rates was particularly striking for Washington because the state’s property crime rate is higher than most.
“It demonstrates just how critical these types of policy changes can be,” Makin said. “I would offer it truly demonstrates why we need empirical data to support these types of studies, so we can understand to what extent crime and communities are influenced as more and more states move to legalization.”
Malkin went on to explain certain limitations of the study, saying “one of the pressing limitations within this study is that not all agencies equally report their clearance rates. It is entirely possible that as we expand our data collection to include additional years, more states, and a wider set of agencies, these results could change.”
The study at Washington State University was funded by the National Institute of Justice, an arm of the U.S. Department of Justice.
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