A federal judge has blocked DuPont Co. from using an expert who once worked for the plaintiffs' lawyers in a case over pollution of Parkersburg city water with the toxic chemical C8.

On Tuesday, District Judge Joseph R. Goodwin disqualified toxicologist Elizabeth Anderson from testifying for DuPont in the pending lawsuit.

The lawsuit seeks alternative drinking water and medical monitoring for customers of the Parkersburg city water system.

Previously, DuPont settled a similar case brought on behalf of thousands of residents who lived in communities around Parkersburg.

Parkersburg residents were left out of that case because at the time, their water supply did not show C8 problems. After new tests found C8 in the city water, a follow-up lawsuit was filed in mid-2006.

While working on the previous case, Cincinnati lawyer Robert Bilott hired Anderson to serve as an expert toxicologist. At the time, Anderson worked for the Alexandria, Va.-based consulting firm Sciences International.

In December, DuPont disclosed it planned to use Anderson as an expert in the new case over Parkersburg city water.

Bilott and other residents' lawyers objected, arguing that DuPont knew Anderson had worked for them and she had confidential information about the plaintiffs' legal strategy. DuPont lawyers say this is a different case, and Anderson had limited involvement in the previous C8 lawsuit.

In an 18-page ruling, Goodwin explained, "litigants, courts and juries have certainly benefited greatly by the guidance and direction provided by expert testimony.

"Although frequently helpful, it is undeniable that 'expert witnessing' is a burgeoning business which is often more lucrative than the usual day job for many experts," Goodwin wrote. "The increased use and importance of experts in litigation has raised numerous questions regarding conflicts of interest."

Goodwin explained that Anderson worked for Bilott at least from November 2001 through February 2002. During that time, Bilott sent Anderson numerous letters and spoke with her on the phone at least 28 times, Goodwin wrote.

"This history of interactions does not indicate a sporadic or informal relationship, but one which involved frequent and seemingly structured communications," Goodwin wrote.

Goodwin concluded Bilott had reason to believe his relationship with Anderson was confidential, and that confidential information was disclosed to Anderson during that relationship.

The ruling, Goodwin said, does not unduly burden DuPont because Anderson was just "one of many proposed experts" for the company.

To contact staff writer Ken Ward Jr., use e-mail or call 348-1702.