Three county attorneys who relied on the troubled St. Paul police crime lab for drug tests will review cases dating back two years.

They're taking the unusual step in light of independent audits released last week that documented widespread problems with staff skills, equipment maintenance and glaring missteps in scientific processes at the lab. The issues first came to light during courtroom testimony last year in Dakota County District Court when public defenders challenged the lab's scientific credibility.

"There clearly has been an understandable drop in the level of confidence in our public about our justice system as a result of these problems," said Dakota County Attorney James Backstrom. "That's unfortunate, but the public should be aware that we are taking this seriously."

In a joint statement released Thursday, Backstrom, Ramsey County Attorney John Choi and Washington County Attorney Pete Orput said they will review cases dating back to July 1, 2010, that resulted in convictions in a jury or court trial. That doesn't include guilty pleas, which make up the majority of drug convictions.

Backstrom said there are 30 to 45 such cases in Dakota and Ramsey counties combined. There are no such cases in Washington County.

The offices will determine if any evidence is available for retesting. If retests show no narcotics, the conviction will be vacated.

If there is no evidence left, the offices will review the court file for any preliminary field tests or corroborating evidence, such as confessions.

The attorneys said they would vacate convictions if there were no positive preliminary tests or if there was insufficient corroborating evidence.

The state public defender's office has identified 1,700 cases in the three counties tied to the crime lab going back two years. Many of those are guilty pleas. Backstrom said the attorneys will consider vacating some of those if the public defender's office brings the cases to their attention and the evidence merits such action.

The Minnesota Bureau of Criminal Apprehension has retested 192 active cases first tested by the police lab. In two cases, the BCA found narcotics where police didn't. In one case, the BCA found no narcotics where police found methamphetamine, resulting in the dismissal of that case.

Backstrom said that despite the concern, there is no evidence of widespread misidentification by the police lab.

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