(CBS4) BRIGHTON, Colo. For the second time in about a year, an Adams County deputy's credibility is being questioned, and the questioning is coming from an unlikely source. The move comes as a result of a CBS4 investigation.

Adams County Sheriff's Department officials said they are once again initiating an internal investigation into deputy Andrew Roth.

The move comes after learning that a state hearing officer has raised questions about the deputy's credibility.

Last year a CBS4 investigation aired a tape of Roth making a police DUI stop on the morning of May 25, 2004. Roth's written reports about what happened seemed out of synch with what was on the tape, and experienced DUI cops questioned the discrepancies

"This report is fiction," said Mark Leone, a recently retired Denver Police lieutenant, last year after he reviewed the deputy's reports and the tape.

Leone was a certified DUI officer, once making 1,600 DUI arrests in a 2 year period.

"The report is completely inconsistent with the behaviors I've seen on tape," Leone said. "From what I've seen on this tape, probable cause did not exist for the stop or for the arrest."

Another tape of a Roth DUI stop has now surfaced, and it is generating similar questions.

In the incident, driver Lyndsay Butterfield was pulled over by Roth. Eventually she took a breath test showing she was legally drunk, with a blood-alcohol level of .082.

At a subsequent state hearing to decide on her drivers license status, Department of Motor Vehicles hearing officer Greg Mahoney listened to Roth, reviewed the deputies reports, and later, reviewed this tape

His conclusions were as follows: "I don't think he -- Roth -- administered what's known as the nystagmus test correctly."

On his report, which was key evidence in court, Roth said Butterfield raised her arms, swayed and put her foot down during the one-legged stand test.

Hearing officer Greg Mahoney said that's not what he saw. "I didn't see her arms being more than, say, 4 inches from her body," he said. "So I don't think he was credible regarding certain aspects of the standard field sobriety tests."

"If an arrest is invalid, everything that flows from it is invalid," said Chris Cessna, the woman's lawyer.

Mahoney concluded by saying "I thought there was a credibility problem with officer Roth in some of the things he said."

"Officers have reputations among the courts (and) among the DA's, and an officer that accrues too many issues of credibility is going to have a very hard time having his cases prosecuted and taken to trial," Cessna said.

Adams County Sheriff Doug Darr declined to talk to the CBS4 Investigates team. However, his spokesman said this has caused the department to launch an internal investigation because "credibility is important in our business. The issues cause us enough concern to want to look into it."

The department has declined to tell CBS4 the outcome of its first investigation into Roth, and they said there is no guarantee they will share the outcome of this one, either.