A former Massachusetts chemist accused of faking test results at a state drug lab has pleaded not guilty at her sixth and final arraignment.

Annie Dookhan was arraigned Monday on a charge of misleading a grand jury prosecutor and judge. She and her attorney declined to comment after the brief hearing. She has been free on $10,000 bail and prosecutors did not ask the judge in Salem to increase it.

Dookhan is accused of falsely claiming she holds a master's degree in chemistry while testifying as an expert witness. She has already pleaded not guilty to a string of charges in five other counties.

Dookhan was indicted in December on a total of 27 charges related to her alleged misconduct at the lab.

The scandal could jeopardize thousands of criminal cases.