HOUSTON -

Troubling testimony emerged in a downtown courtroom Thursday that questions the validity of thousands of drug tests conducted by the Harris County Community Supervision and Corrections Department.

The main thrust of questions center on whether urine samples used to drug test Harris County probationers are being handled properly.

"There are no safeguards, there's a lot of human error," said attorney Lisa Andrews.

Andrews has called several witnesses to testify at this hearing including the head of the department, Paul Becker. Probationers are required to submit to drug tests. If a person tests positive for drug use then their probation can be revoked and they can be sent to jail.

"It's riddled with errors, there's no chain of custody," said Andrews following the first day of testimony.

In fact, a current employee of the department testified that frequent mistakes has led him to question test results.

"I can't rely on the information I get from the (urine analysis) lab," probation officer Donahue Schacherer testified. "From my perspective there is no chain of custody."

Another witness was the supervisor of the independent lab used by the department to verify whether a probationer has tested positive for drug use. Steve Harris testified that data entry mistakes by the department led to at least 31 cases of test results being linked to the wrong person.

Harris told the court he warned the department numerous times that not enough personal information was being included with urine samples to ensure test results were linked to the correct person. Harris also testified that it was not uncommon for the lab to receive urine samples with no "chain of custody" form. These forms help ensure that test results are linked to the correct person's sample.

During an interview with Local 2, Becker responded to questions as to whether he knew of sloppy testing procedures leading to the wrong person being sent back to jail.

"I have no idea," Becker said. "Not that I'm aware of, I have no idea."

Becker added he does not believe the drug testing program is in disarray. Becker has been subpoenaed to testify during this hearing, which will continue Friday.

The District Attorney's Office also sent a written statement to Local 2 since prosecutors have to rely on these test results when deciding whether to seek a revocation of a person's probation.

"At the conclusion of this hearing, we will thoroughly review any allegations raised," the statement read.