SEATTLE -

A primary backer of Washington's legalization of marijuana is reporting a massive drop in pot possession charges last year.

The state chapter of the American Civil Liberties Union says court filings for misdemeanor marijuana possession by adults over 21 years old totaled just 120 cases in 2013, a huge drop from 5,531 cases in 2012. The 120 cases filed last year likely concerned people caught with more than the ounce of weed they're allowed to have under Washington law, but less than 40 grams, which can trigger felony possession charges.

ACLU lawyer Mark Cooke says the data suggest legalization has helped free up police and prosecutorial resources.

But the organization also says racial bias concerns persist: Among the 120 cases last year, African American adults remained almost three times more likely than whites to face charges.