A recent analysis published in the Criminal Justice Ethics academic journal suggests when technicians perform forensic analysis of blood and other evidence for cases such as drunk driving, the results can be influenced by built-in financial incentives to produce a conviction. If false conviction rates are very low, a 3 percent error rate could put 33,000 innocent individuals behind bars (in the U.S.) every year.
The primary problem, according to the paper, is that fourteen states reward crime labs with a bonus for each conviction they generate. When there is a reward for a guilty result, a lab technician will not double-check test results that are in the guilty range, though he would be more likely to double-check results that show innocence.
For example, in 2009, a crime lab in Colorado Springs, Colorado was caught certifying at least 82 DUI blood tests with falsely high readings. A whistleblower in Washington, DC revealed in 2010 that the city had been using faulty breathalyzer machines for more than a decade.
View the full text at http://www.tandfonline.com/doi/full/10.1080/0731129X.2013.817070