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Prosecutors won't charge former Northern Colorado DNA forensic analyst who had history of errors in work

Weld County District Attorney will not prosecute forensic DNA analyst fired over possible anomolies
Weld County District Attorney will not prosecute forensic DNA analyst fired over possible anomolies 03:10

Months after being fired for having a series of anomalies in her work, former Weld County Sheriff Office DNA analyst Chiara Wuensch learned she will not face criminal charges in Weld County. 

The announcement, made by Weld County District Attorney Michael Rourke, comes after the Colorado Bureau of Investigation identified errors in Wuensch's work at a Northern Colorado testing lab.

"There were approximately 2,000 DNA samples that she had tested that CBI and the Weld County Sheriff's Office looked at to determine how many anomalies happened," Rourke said.


CBS News Colorado's Dillon Thomas learned, of the roughly 2,000 DNA samples reviewed by investigators, only five errors were identified. However, investigators clearly believed those five were too many given they could result in prosecutions being altered.

The Weld County Sheriff's Office fired her shortly after the errors were first reported, Sheriff Steve Reams said he planned to press charges against Wuensch as a result of the errors.

However, Rourke said, after months of reviews, the errors made did not appear to have criminal intent nor did they result in any major inaccuracies when it came to court cases.

"When there is any information that can call into question the credibility of that evidence, that is something we take very seriously," Rourke said.

According to prosecutors, some of the errors identified in the work done by Wuensch were identified with the Microsoft program Excel.

Roruke said his office spent many hours working to assure Wuensch's errors within Excel didn't progress anywhere else in her work.


"Did any of these anomalies impact any criminal prosecution, criminal investigation, both past and present? We wanted to make sure there were no concerns with the credibility or truthfulness of the information that may have led to the conviction of an offender," Rourke said.

After completing their investigation, Rourke said the office believes some of the errors were simply mistakes that were the result of inadequate knowledge of how to operate Excel. He said it would've been a greater concern if the errors were more common and had an apparent criminal intent behind them. However, the DA's office determined Wuensch continued to do the rest of her work as expected even after having the errors, suggesting she didn't realize she was inputting data incorrectly in some cases.

"We declined to file charges," Rourke said. "Had we seen that these anomalies existed, that these deletions or modifications to the spread sheet had occurred for the purpose of avoiding additional work, cutting corners or trying to increase efficiency, that would have been a different story."

CBS News Colorado reached out to the Weld County Sheriff's Office seeking interview or comment on the DA office's decision to not prosecute. A spokesperson declined to comment and deferred comment back to the DA's office.


Rourke said Wuensch wasn't criminally culpable. However, he admitted this investigation will cause some to now be skeptical of those analyzing their DNA in criminal cases.

Rourke said a few inmates, or their lawyers, have already raised some questions. He said his office is no longer concerned that Wuensch's work caused anyone to be wrongfully prosecuted or sentenced. 

"This is going to give an opportunity for defense attorneys or criminal defendants to question the forensic sciences that may have been utilized in their cases," Rourke said.

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