Updated

Massachusetts' highest court has dismissed more than 21,000 drug convictions because of misconduct by a chemist who tested evidence in a state lab.

Lawyers who fought for the cases to be dismissed call the ruling a historic victory for justice and fairness, but are countering fears that dangerous criminals might soon walk free from state prisons.

They say few prison doors will swing open as a result, since most defendants had either completed their sentences or were never given prison time to start with.

Annie Dookhan was accused of manipulating drug tests and falsifying results. She pleaded guilty in 2013 to charges she tampered with evidence and falsified results.

After a five-year legal battle led by the American Civil Liberties Union, the court Thursday approved the dismissal of 21,587 convictions.