The Houston Forensic Science Center will review its policies after three separate incidents where evidence samples were contaminated. The actual results of the tests in the three incidents were not affected because there were other uncontaminated samples that were testable. However, these incidents prompted officials to review the lab’s quality control.  “In addition to suggesting policy revisions, the [Office of Inspector General] urged the Houston Forensic Science Center to address error review in regularly scheduled staff meetings, retrain staff, ensure contractors understand their quality control responsibilities and self-disclose errors to the state’s forensic science commission.”

http://www.chron.com/news/houston-texas/houston/article/Houston-crime-lab-revises-policies-after-7062924.php