Special court sessions are set to begin the week of Oct. 15 to hear a flood of legal challenges by drug defendants in the wake of a scandal at a Massachusetts drug-testing lab.

Former state chemist Annie Dookhan is charged with obstruction of justice for allegedly failing to follow testing protocols and altering results at the now-closed lab.

Judge Christine McEvoy is expected to hear requests to reduce bail, put sentences on hold and to withdraw guilty pleas from up to 180 people who are currently serving time in county jails or state prisons in cases where Dookhan was involved in testing evidence. The sessions in Suffolk Superior Court are scheduled to begin on Oct. 15 and run through Oct. 26.

Similar sessions have been scheduled in courts around the state to hear additional challenges.