Greg Taylor served 16 years in prison after he was falsely convicted of murdering a prostitute in Raleigh, North Carolina. He was released in February by a special three-judge panel after it was discovered the blood police claimed to have found in his SUV wasn't blood at all. In the wake of that debacle, North Carolina Attorney General Roy Cooper ordered two retired FBI agents to conduct an investigation on the State Bureau of Investigation (SBI) crime lab. The report came out last week, and it is damning.

The report found that SBI agents withheld exculpatory evidence or distorted evidence in more than 230 cases over a 16-year period. Three of those cases resulted in execution. There was widespread lying, corruption, and pressure from prosecutors and other law enforcement officials on crime lab analysts to produce results that would help secure convictions. And the pressure worked.

A stunning accompanying investigation by the Raleigh News & Observer found that though the crime lab's results were presented to juries with the authoritativeness of science, laboratory procedures were geared toward just one outcome: putting as many people in prison as possible. The paper discovered an astonishingly frank 2007 training manual for analysts, still in use as of last week, instructing researchers that "A good reputation and calm demeanor also enhances an analyst's conviction rate." Defense attorneys, the manual warned, often "put words into the analyst's mouth to try and raise inaccuracies." The guide also instructs analysts to beware of "defense whores"—analysts hired by defense attorneys to challenge their testimony.

Forensic science in America is corrupted by a fundamental conflict of interest. In far too many states, crime labs fall under the auspices of law enforcement, usually reporting to the state attorney general. A forensic analyst's real aim should be to follow the science, even if results prove disappointing to bosses who are trying to secure convictions. But the pressure from prosecutors, even when it's not overt (which it often is), produces bias even in the work of the most fair-minded analysts.

The relationships between SBI crime lab researchers and North Carolina prosecutors aren't just cozy, they're downright cuddly. The News & Observer reports that in one case two blood-spatter specialists ran through multiple experiments in order to produce even one that would make the blood patterns on a defendant's shorts support the prosecution's case. The two analysts are seen on video high-fiving after finally producing the desired result.

For those clinging to the notion that analysis in a law enforcement-managed laboratory can be independent, the newspaper uncovered prosecutor reviews of crime lab analysts indicating the contrary. In 2003, for example, prosecutor Ann Kirby, wrote in a review of a drug analyst, "If Lisa Edwards gets any better on the witness stand, the Johnston County defense bar is going to try and have her banned from the county!"

These weren't a few rogue analysts; the crime lab's problems extend across a wide array of forensic disciplines. Until 1997, the lab's serology unit didn't release negative test results as a matter of policy. If tests showed that a substance that police claimed was blood wasn't in fact blood, analysts simply kept those results to themselves.

Greg Taylor was wrongly convicted precisely because of this policy. A substance that police falsely identified as blood was found in Taylor's truck. But the field tests that police use to find blood at a crime scene have a high margin for error. More sophisticated lab tests showed that the substance wasn't blood, but a SBI analyst testified at Taylor's innocence hearing that technicians were told to ignore these tests if they contradicted the field-test results.

In another case, an attorney for a woman accused of killing her mother was shocked to learn that the lab's DNA tests on blood found at the crime scene matched his client. He called the lab and asked them to retest. They refused. He was finally able to obtain a court order for a new test. It was negative. It turned out that a lab technician had swapped the sample provided by his client with blood taken from the crime scene.

The SBI crime lab scandal is only the most recent story of forensics malfeasance. In recent years there have been forensics scandals in Virginia, Maryland, Mississippi, Oklahoma, Nebraska, California, Michigan, Texas, and at the FBI. And this is only a partial list. At some point, it becomes sensible to conclude that these scandals aren't the result of isolated bad actors, but of a system that produces them.

Last year the National Academy of Sciences released a scathing report on the use of forensics in the courtroom, finding systemic problems ranging from analysts routinely overstating the implications of their test results, to the widespread use of forensic specialties like bite-mark analysis that have little basis in science at all.

Most forensic disciplines were invented by police investigators, not scientists. Courts have allowed these disciplines to be admitted into evidence before they've been subjected to any serious scrutiny from the scientific community. The methods used in most crime labs disregard critical scientific principles such as blind testing, competency testing, peer review, and statistical analysis. Yet when a forensic specialist testifies in the courtroom, his testimony usually carries the weight and veneer of actual science. (See here for some suggested reforms.)

North Carolina Attorney General Roy Cooper is a good illustration of the political hurdles standing in the way of fixing any of these problems. Cooper deserves praise for ordering such a comprehensive investigation. It takes guts for a politican to risk being labeled "soft on crime," especially a politician who is a current or former prosecutor.

Still, Cooper was made aware of the problems in SBI as long ago as 2005, when he was pressed by local media and activists to look into how Floyd Brown, a developmentally disabled man who can't recite the alphabet past the letter K, was able to articulate to SBI investigators a detailed confession about how he murdered an elderly woman in his neighborhood. Brown seved 14 years in a mental institution before he was exonerated in 2007. Cooper didn't order an investigation into Brown's case until last year, and even then only in the face of a lawsuit.

And even after Cooper's own damning report and the series of follow-on investigations by the News & Observer, Cooper is treating the SBI scandal as if it were a series of isolated cases and not a systemic problem. Cooper told the paper he sees nothing wrong with lab researchers consulting with prosecutors before performing their analysis, a practice proven to produce biased test results (SBI analysts are also discouraged from consulting with defense attorneys). He also objected to moving the crime lab to a different government agency so that analysts wouldn't be reporting to prosecutors, telling the News & Observer, "You don't want to hobble law enforcement by removing key tools such as technology to prevent them from solving crime." No, you don't. But moving the lab wouldn't do that. It would merely prevent analysts from feeling they need to please prosecutors by providing them with favorable test results.

So will the lab at least open itself to peer review and observation? John Watters, a 17-year veteran of North Carolina's Department of Justice who, as the News & Observer reports, "fights requests for information not specifically listed in the discovery law that ensures that defense attorneys have access to investigative reports," told the paper he'll resist any effort to allow outsiders to evaluate the lab's work. In fact, the lab banned outside observers in 2009. In a hearing the same year, Watters explained his reasoning:

"I'm telling you that the thing that concerns us most is the precedent this would set, and the potential for harm…we've never been a testing laboratory for the defendant. We are the state's laboratory."

So long as government officials retain that mindset, we'll continue to see forensic scandals like the one currently unfolding in North Carolina. Which means preventable mistakes will continue to send innocent people to prison, and allow guilty people to remain free.

Radley Balko is a senior editor at Reason magazine.