95% of drug convictions that came with a drug test were fixed by Annie Dookhan, a chemist for the Department of Public Health. Prosecutors for the seven districts in Massachusetts agreed to drop 20,000 drug charges due to this scandal according to YAHOO.
Dookhan was handling drug tests for drug convictions from 2003 to 2012 and investigators found that she was contaminating drug samples, fixing results and mishandling evidence. Some were intentionally done to turn a failed test to a passing test.
She was convicted in 2013 and is serving a 3 to 5 year sentence.