( CNN ) -- A report by the Massachusetts inspector general released Tuesday said that former drug lab technician Annie Dookhan was the `` sole bad actor '' at a Boston drug lab once responsible for tests related to thousands of criminal cases , and that directors of the facility were `` ill-suited '' to oversee her and other lab technicians . The state of Massachusetts says Dookhan doctored evidence to change test results at the Hinton State Drug Laboratory . After Dookhan 's co-workers told state police her work might be unreliable , the state attorney general 's office began investigating the case in July 2012 . The tampering called into question at least 40,000 cases going back to 2003 and , in some cases , may have wrongfully convicted the innocent . She was found guilty of multiple charges related to the case , including obstruction of justice , mishandling of drug evidence and lying about holding a master 's degree in chemistry from the University of Massachusetts . She was sentenced in November of last year to three to five years in prison . `` Dookhan was the sole bad actor at the Drug Lab . Though many of the chemists worked alongside Dookhan for years , the OIG ( Office of the Inspector General ) found no evidence that any other chemist at the Drug Lab committed any malfeasance with respect to testing evidence or knowingly aided Dookhan in committing her malfeasance , '' the report said . But the report did n't stop short of blaming the unprecedented breach in confidence solely on Dookhan . `` The directors were ill-suited to oversee a forensic drug lab , provided almost no supervision , were habitually unresponsive to chemists ' complaints and suspicions , and severely downplayed Dookhan 's major breach in chain-of-custody protocol upon discovering it , '' according to the inspector general 's report . The Inspector General 's Office reviewed more than 200,000 documents -- including e-mails , lab results and lab records -- and interviewed more than 40 people who worked with the drug lab to check for deficiencies , the report said . An investigation by Inspector General Glenn Cunha and his office showed that former Department of Public Health Commissioner `` John Auerbach and his staff failed to respond appropriately to the report of Dookhan 's breach of protocol '' and `` the investigation DPH conducted was far too narrow , '' the report said . Gov . Deval Patrick closed the lab , in Boston 's Jamaica Plain neighborhood , in August 2012 . That year , Auerbach submitted his letter of resignation from the Public Health Department to Patrick amid the investigation , and the Massachusetts State Police now oversee all of the state 's drug cases . The Inspector General 's Office concluded that `` all samples in which Dookhan was the primary chemist should be treated as suspect and be subject to careful review . '' In addition to the drug samples Dookhan mishandled , an additional 2,000 drug samples not handled by Dookhan were found to potentially contain `` exculpatory evidence '' to defendants in criminal cases because the drug lab failed to disclose `` additional , inconsistent testing results , '' the report said . The Inspector General 's Office says it is retesting these samples and will give prosecutors and defendants accurate information about the tests when they 're completed . In November 2012 , Donta Hood , who was convicted of a cocaine charge in 2009 , was released from prison after his defense team questioned the validity of Dookhan 's testing results and her expert testimony . After his release , he was arrested on a gun possession charge . While on bail for that charge , he was arrested and charged with the murder of Charles Evans , 45 , the Brockton Police Department said . Hood is awaiting trial on the murder charge . The next hearing in this case is a motions hearing on March 11 , the Brockton Superior Court Criminal Clerk 's Office said .
The drug lab was once responsible for tests related to thousands of criminal cases . Massachusetts says Annie Dookhan used drugs to change test results at the lab . Lab technicians were ` ` ill - equipped '' to oversee her and other lab technicians , the report says . Massachusetts , found guilty of multiple charges in the case , was sentenced to prison in Massachusetts .