SALEM, Mass. (AP) ? A former Massachusetts chemist accused of faking test results at a state drug lab faces her sixth arraignment.

Annie Dookhan is scheduled to be arraigned Monday on an obstruction of justice charge in Salem Superior Court. She is accused of falsely claiming she holds a master’s degree in chemistry while testifying as an expert witness. Dookhan 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 a state drug lab. Authorities have said she told state police she sometimes would take 15 to 25 samples, test only five of them, but then list them all as positive for cocaine.

The scandal could jeopardize thousands of criminal cases.

Copyright 2013 The Associated Press.