We all know that the CSI television shows bear little resemblance to reality. Real-life medical examiners don’t go into the field, don’t confront and intimidate suspects, don’t comfort grieving relatives, don’t carry guns…and don’t wear designer clothes to the office. They don’t wrap up their cases in an hour. And they don’t solve every case.

Now comes troubling news that some medical examiners lack another characteristic of their television counterparts – scientific integrity.

An ongoing investigation in North Carolina has revealed that agents at the State Bureau of Investigation lab, or SBI, have corrupted their science to suit the prosecution. They misinterpreted blood stain patterns, re-ran experiments until they got “right” results, neglected to conduct important laboratory tests, and conducted phony blood analyses. The result: more than 200 wrongful convictions. (You can read continuing coverage of the scandal here.) Three people were wrongfully executed.

In San Francisco, a criminalist in the city’s crime lab has been skimming cocaine from the evidence room for years. Her evidence-tampering revealed such lax accounting and security measures that the state has invalidated many convictions and has slammed the drug prosecution process to a halt. A local public defender described it as a “tsunami of incompetence” – so severe that the lab had to be closed and drug cases handled by another facility. At least 750 cases have been dismissed.

Houston’s crime lab has been wracked by one scandal after another. In 2003 the police department’s DNA lab was found to be so error-prone that the city shut it down. It re-opened, only to be closed again several years later. This year a team of outside consultants found technical errors 62 percent of the department’s fingerprint cases.

Detroit closed its crime lab in 2008 after reviewers found a “shocking level of incompetence.” All Detroit’s CSI work now goes to the state crime lab, which further the state’s already-strained resources.

Problems in the nation’s crime labs have been festering for years. Surveys of the nation’s crime labs have shown nothing like the models we see on TV, with their state-of-the- art equipment and futuristic efficiency. Most lack modern equipment and standardized procedures, and face enormous backlogs of cases. But the most insidious problems involve the culture of certain crime labs – a culture that seems more concerned with closing cases than bringing scientific truth to criminal investigations.

Most crime labs are housed in police departments, administratively if not physically. The technicians may be civilians, but their paychecks and orders come from the police. This situation biases their results. Consciously or not, technicians want to produce results that will help the police. Current procedures encourage that tendency. When police give a sample of evidence to lab workers, they identify it as coming from a suspect. The investigator knows what result is desired and feels pressure to interpret in that direction.

This phenomenon is known as a “context problem” in scientific research, and behavioral experts have been studying it for years. The most recent study, published last January in the journal Law, Probability and Risk, noted that even the most honest forensic examiners are influenced by prosecutors and police, who “implicitly convey information” by the way they submit and identify samples. According to Michael.J. Saks, a leading scholar in the area of forensic, even this subtle communication has, “a small but relentless impact on perception, judgment, and decision-making.”

When multiplied by the enormous caseload crime labs have handled every year, this problem has caused hundreds wrongful convictions, and several executions.

There are solutions to this problem, but they’re not easy or cheap. The National Academy of Sciences recommends that forensics labs should be separated from justice departments and reinstated as individual entities – an expensive proposition, that is not particularly appealing to police.

A less expensive, intermediate solution would be to follow the procedures used in other branches of science. In medical testing, for example, researchers use “double-blind” studies to ensure objectivity. Neither the recipients of an experimental medicine nor the doctors who test them know which patients received the experimental drug and which received the placebo. Both sides are “blind” to the experimental variable: the subject doesn’t convey information with his or her behavior, and the scientist doesn’t interpret the experiment based on the expected or desired results.

It’s time for forensic scientists to adopt the same procedures. Rather than receive samples identified by police as coming from a “suspect”, the technicians should receive samples labeled with a code so they don’t know the origin. With no knowledge of the source, they would be more likely to objectively report results. In order to reduce the sense of belonging to a side, they should report the results to both prosecutors and defense attorneys. This step would go a long way to making sure that science informs the investigative process, as opposed to being corrupted by it.