DALLAS — Thousands of DWI convictions in North Texas could be jeopardized after the testimony of a state forensic scientist recently came under scrutiny, according to a newspaper report.

Christopher Youngkin was involved in a 2013 lab error in which two blood samples from separate cases were mixed up. Youngkin erroneously reported to police that a woman had a blood-alcohol level that was nearly twice the legal limit when in fact she had not been drinking, The Dallas Morning News reported (http://bit.ly/2e9QSVF ).

Attorneys now are questioning whether Youngkin in recent cases has given conflicting testimony about the error, which would call into question his credibility as a witness and expert.

Youngkin works for the Texas Department of Public Safety crime lab in the Dallas suburb of Garland. He took the stand Wednesday in a misdemeanor case of driving while intoxicated and ended up invoking his Fifth Amendment right not to testify.

A DPS spokesman on Friday declined to answer the newspaper’s questions about Youngkin or the issues raised by defense attorneys, saying it would be inappropriate to comment at this time.

Defense attorney Hunter Biederman said a Dallas County jury found a client not guilty of drunken driving last month, in part, he believes, because of cross-examination of Youngkin over his lab error.

“Most people haven’t had the opportunity to know about this and either use it in trial, use it in pre-negotiations or use it in punishment,” he said.

There’s no guarantee of getting an acquittal, Beiderman said, but the questions raised about it could lead to conviction of a lesser offense, which means a less severe punishment.

The scrutiny of Youngkin comes after a Harris County toxicologist last month resigned when her academic qualifications were questioned. The toxicologist, Dr. Fessessework Guale, had worked in the county medical examiner’s office since 2006 and had regularly testified in Houston-area DWI cases.

She earlier had been reassigned after officials learned that she testified to having a master’s degree in toxicology but actually earned one in physiological science from Oklahoma State’s veterinary school.

The district attorney’s office has sent letters inviting defense attorneys representing thousands of DWI defendants in Harris County to request reviews of cases involving Guale’s testimony.

Information from: The Dallas Morning News, http://www.dallasnews.com