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Conservative law enforcement officials ranging from local sheriffs to Attorney General Jeff Sessions have long argued that cannabis legalization is a gateway to increased crime, but scientific evidence is increasingly proving that such claims are unfounded. Marijuana advocates — and even some wiser members of the law enforcement community — have argued that putting an end to prohibition would actually reduce crime by giving police additional time and money to enforce more serious offenses, but to date there has been little research to support or deny this claim.

Until now, that is. New research recently published in the journal Police Quarterly finds that cops in Washington and Colorado have been solving more crimes since those states legalized marijuana. Both states reported seeing post-legalization increases in their police clearance rates — the number of crimes resulting in a arrest compared to the total number of reported offenses, according to Marijuana Moment. Clearance rates for violent crimes had been steadily declining in Colorado and Washington at the beginning of the decade, but after both states legalized pot in 2012, these rates soon leveled out and began to increase.

“This set of findings suggests that right around the time of legalization, clearance [rate] trends seemed to increase for violent crime in general for both Colorado and Washington, though no similar shifts are noted for the country as a whole,” the study reports. Similarly, even as overall clearance rates for property crimes have been decreasing across the U.S., police in these two states reported an increase in solved property offenses.

“While our results cannot specifically explain why police clearance rates have increased in Colorado and Washington, we think the argument that legalization did in fact produce a measurable impact on clearance rates is plausible,” the researchers concluded. “Our models show no negative effects of legalization and, instead, indicate that crime clearance rates for at least some types of crime are increasing faster in states that legalized than in those that did not.”

Although this is the first study focusing on the rates of crime clearance in canna-legal states, other research has identified a growing number of connections between legal pot and crime reduction. In 2014, researchers at the University of Texas found that all 11 states with legal medical cannabis before 2006 reported reduced rates of homicides and assaults. Last year, another study confirmed that states that enacted medical marijuana programs by 2015 saw reductions in the rates of murders and robberies. Further research found that medical cannabis dispensaries attract less crime to their neighborhoods than alcohol or tobacco stores.

Despite prohibitionists' claims, the body of research connecting marijuana legalization with crime reduction is continuing to grow. FBI statistics have confirmed that the total number of violent offenses reported in Washington has decreased since the state legalized adult-use cannabis. Earlier this year, a study investigating crime in U.S. states bordering Mexico found that states with legal medical marijuana had lower crime rates than those that did not. Another study looked at neighboring counties on the Washington-Oregon border from 2012 to 2014, and found that there were fewer rapes and property crimes in Washington, where pot was legal, than in adjacent Oregon counties, where the plant was still illegal at the time.