A grand jury investigating the Harris County District Attorney's Office found no criminal conduct in connection with the Houston Police Department's breath-alcohol testing vehicles, but the grand jury foreman and the district attorney had harsh words for each other.

Questions about the accuracy of driving while intoxicated tests performed by the vans were raised by a former HPD lab supervisor in 2011. In October, a grand jury began investigating to determine if prosecutors knew the test data they were using to prosecute accused drunken drivers might be flawed.

The district attorney's office was barred from the proceedings because members of the office were under investigation.

The grand jury's foreman, Trisha Pollard, released a statement critical of the district attorney's office, saying that prosecutors resisted attempts to initiate the investigation. The statement also said the grand jury investigation was distracted by the assistant district attorney most responsible for the prosecution -- she invoked her Fifth Amendment right against self incrimination.

Pollard said grand jurors were harassed and investigated by members of the district attorney's office.

"The stain upon the Harris County District Attorney's Office will remain regardless of any media statement issued or press conferences performed by anyone," Pollard wrote.

District Attorney Pat Lykos said Pollard's statement was not about the law, but it was about election-year politics.

"I will not let the honor and integrity of this office and of me be impugned or compromised," Lykos said. "We will not be slandered nor libeled."

Lykos described the grand jury's investigation as a political attack punctuated with frequent leaks to the media.

"It's an outrage, it's an abuse of power and a corruption of the criminal justice system," Lykos said.

Lykos said no grand jurors were harassed or investigated.