The highest court in Massachusetts has formally approved the dismissal of more than 21,000 drug convictions that were tainted by the misconduct of a former state drug lab chemist.

The American Civil Liberties Union of Massachusetts says the final order from the Supreme Judicial Court on Thursday marks the single largest dismissal of convictions in U.S. history.

The action by the court was expected after seven district attorneys in eastern Massachusetts submitted lists on Tuesday totaling 21,587 cases they would be unwilling or unable to prosecute if new trials were ordered.

The cases were called into question when chemist Annie Dookhan was charged with tampering with evidence and falsifying drug tests. Dookhan pleaded guilty to perjury and other charges in 2013 and served a three-year prison sentence.

White officer headed to court ahead of civil rights trial

A white former South Carolina police officer charged in the death of an unarmed black motorist is expected in court as his federal trial approaches.

A motions hearing is scheduled Friday in the case against 35-year-old Michael Slager.

Slager's federal civil rights trial in the death of 50-year-old Walter Scott starts next month. Another hearing is scheduled for Monday, when attorneys will discuss the admission of certain experts to testify.

Last month, a federal judge ruled prosecutors may show jurors video of the former North Charleston officer shooting Scott. The bystander's cellphone video was viewed millions of times around the world.

Slager also faces murder charges in state court, where his first trial ended in a hung jury. His retrial is scheduled for August.