A Massachusetts chemist accused of faking drug test results, forging paperwork and mixing samples at a state police lab was arrested Friday in a scandal that has thrown thousands of criminal cases into doubt.

Annie Dookhan, 34, was led to a state police cruiser at her home in Franklin, about 40 miles southwest of Boston. Dookhan's alleged mishandling of drug samples prompted the shutdown of the Hinton State

Laboratory Institute in Boston last month and resulted in the resignation of three officials, including the state's public health commissioner.