Maryland Marijuana Policy Only Accounts for 17% of Drop in Baltimore Arrests

February 3, 2016

When looking at Baltimore Police Department (BPD) arrest statistics it’s important to note that in Maryland possession of less than 10 grams of marijuana is no longer grounds for arrest, effective October 1, 2014. When looking at the drop in arrests from 2014 to 2015 we can at least expect to attribute a portion of the drop to the change in marijuana policy. But exactly how much?

10,616 fewer arrests in 2015

My previous estimate was that we’d finish the year with about 10,000 fewer arrests in Baltimore in 2015 compared to 2014. The final tally is shown at right, indicating the drop between 2014 and 2015 was 10,616, or a 28.8% decrease.

Marijuana-related arrests have been declining since 2013, falling from 13.6% of all arrests to just under 2%.

Policy change effect on arrests

Out of the 10,616 fewer arrests in 2015, what portion are due to the drop in marijuana arrests? Looking at all marijuana-related arrests, the number is about 25.9%. Looking at only the charge for possession of less than 10 grams (which is the charge that we should see practically zero of in 2015 due to the policy change), the portion is only about 17%. (There were about 1,812 fewer arrests for this charge in 2015 which is about 17% of the 10,616 fewer total arrests.)

This is of course only the arrests for which possession of 10 grams of marijuana was the charge. I’m guessing that possession of marijuana used to be the open door for police to nab people for other offenses, so while only 17% is directly attributable, a larger portion of the drop in arrests might be attributed indirectly to the change in marijuana policy - of course, merely a guess.

BPD arrests data obtained from Open Baltimore, data downloaded January 7, 2016.
Analysis conducted using Python, Pandas, and Plot.ly.
Full analysis Jupyter (iPython) notebook can be found here.

Maryland Marijuana Policy Only Accounts for 17% of Drop in Baltimore Arrests - February 3, 2016 - Justin Elszasz