Prosecutors have dismissed a Ramsey County drug case after state tests revealed that the embattled St. Paul crime lab erroneously identified a substance as methamphetamine.

The drug possession charge against Pahoua Yang, 26, of St. Paul, is the first to be dropped since major failings in the lab's work were revealed during a July court hearing, leading authorities in Ramsey, Dakota and Washington counties to ask the state Bureau of Criminal Apprehension to review test results.

The state has completed new tests on nearly 100 cases, but dozens more remain.

"We are understandably troubled by the conflicting results reached in the Yang case," three county attorneys -- John Choi of Ramsey, James Backstrom of Dakota and Pete Orput of Washington -- wrote to St. Paul Police Chief Thomas Smith last week.

"We welcome your action to immediately review the circumstances regarding the initial testing and retesting of the substance in the Yang case and share the results of that review with us and the public."

Smith suspended drug testing at the lab immediately after the revelations triggered an outside review.

With the suspension of drug testing at the St. Paul lab, the three affected counties together have submitted 271 new drug cases for testing since mid-July, BCA spokeswoman Jill Oliveira said. In the same period last year, those counties had submitted 30 cases to the BCA.

The BCA has completed about 215 of nearly 450 new or retested drug cases from the three counties, clearing most of them in about 60 days, Oliveira said.

According to charges filed against Yang in August 2011, the St. Paul crime lab's "preliminary presumptive examination" of evidence taken from Yang's jacket showed .38 grams of methamphetamine.

The BCA reported that what they found was not a controlled substance but a material commonly used to cut meth, Choi said.

"There was always that possibility," he said. "We certainly didn't want to hear that."

Ramsey County prosecutors were notified Sept. 25 that BCA tests in the Yang case did not detect narcotics. They dropped the charges two days later.

Questions raised in July

St. Paul police spokesman Howie Padilla said the department is looking into what happened in the Yang case.

"As soon as we found out about the conflicting results, we launched our own investigation," he said, adding that he could not elaborate because the investigation is pending.

Public defenders Lauri Traub and Christine Funk began challenging the crime lab's credibility in July.

Testimony in Dakota County District Court revealed that lab staffers didn't follow standard operating procedures or seek second opinions on questionable results.

A slew of other mistakes were revealed, as well. Defense experts testified that the lab did not have secure evidence handling and that key equipment was poorly maintained.

One lab criminalist testified that she sometimes used the same tool on multiple samples. A co-worker then testified that she always used new tools to avoid contamination.

The last day of testimony associated with the lab problems will resume Oct. 23 and possibly continue the next day.

Traub and Funk initially sought to throw out the crime lab's results in a handful of cases, but the focus now has shifted to whether the lab's questionable handling of evidence should prevent the BCA from retesting samples in four cases.

Judge Kathryn Messerich Davis' decision will only have an immediate effect on the four cases.

Yang also isn't off the hook yet, as she is scheduled to go to trial later this week on separate drug charges.

She was charged in March with fifth-degree drug possession when an officer stopped her for not wearing a seatbelt. After she was brought to the county jail on two outstanding warrants, she told the officer she had a small bag of meth in her bra, according to the complaint. The St. Paul police crime lab tested it and found .69 grams of meth.

She could not be reached for comment Monday.

Chao Xiong • 612-270-4708 Twitter: @ChaoStrib