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New York City police boosted arrests for public possession of marijuana in recent years, on the assumption that the action would improve public safety.

According to a report from the Human Rights Watch, however, that logic may not be justified. The group tracked for seven years nearly 30,000 New Yorkers without prior criminal convictions who were arrested for minor marijuana possession in 2003 and 2004, and found only 3.1% of those arrested are later convicted of a violent felony.

Government statistics show that officers arrested nearly 600,000 people for marijuana possession between 1996 and 2011, as part of the city’s strategy to concentrate on petty crimes. By doing so, police hoped to catch the people who were most likely to already be committing more serious offenses (and evading detection) or who would do so again in the future. In that time, marijuana possession was the most common charge in New York City court cases.

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The arrests primarily targeted black and Hispanic violators, the report confirmed. Seventeen percent of those arrested during the study period were white, while blacks made up 49% and Hispanics constitute 31% of those charged. Other research on the city’s marijuana arrests shows that between 2004 and 2008, blacks were eight times more likely than whites to be arrested for marijuana possession and Hispanics four times more likely.

The authors note that while New York experienced a drop in crime during the time of the escalated cannabis arrests from the 90s onwards, other cities that used different approaches such as community-based policing and gang outreach to improve public safety did so as well. And a study [PDF] that broke down marijuana arrests and crime rates at the level of precincts found no association between the two.

The Human Rights Watch study found that the felony conviction rate of people arrested for marijuana in New York was actually lower than the national rate, after controlling for age, race and gender. In other words, using marijuana arrests to capture violent criminals may be less effective than simply randomly arresting young men, the group most likely to commit any type of crime.

And the consequences of arrest can have a significant impact on public health. For one, they can lead to job loss and chronic unemployment, since convictions can damage future employment prospects. That in turn can interfere with not only access to health insurance but also with economic status, which is correlated with behaviors that promote better health. Secondly, jails themselves are a source of infectious disease and put people at risk for sexual assault. Teens and young adults— who are the majority of those arrested— can seriously put their health and lives at risk through encounters with the justice system. Finally, arrests can lead to loss of child custody and housing, both of which can harm health.

In 2010 alone, New York City spent $75 million on arresting people for marijuana possession, yet the state continues to have a slightly higher than average level of marijuana use among teens — 14% of youth aged 12-17 smoked in the past year, compared to the national average of 13%. National studies have repeatedly shown that spending on drug enforcement, which rises with rising arrests rates, is not well correlated with addiction rates. Whether the goal is fighting addiction or fighting crime, we may need to use a different strategy.

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