U.S. District Judge Gregory Frizzell ruled Wednesday in Tulsa that the research methods used by one state expert witness, geochemist Roger Olsen, were “subjective” and that his conclusions were “unreliable.”

The ruling follows a similar decision by Frizzell on Tuesday to exclude the testimony of another state expert witness.

The decisions are the latest in a string of recent pretrial court victories for 13 poultry companies that Attorney General Drew Edmondson sued in 2005.

He claims that they are legally responsible for the handling and disposal of poultry waste that has damaged portions of the Illinois River watershed in Oklahoma.

The poultry industry was successful last week in its claim that the state couldn’t recover monetary damages totaling more than $600 million because the Cherokee Nation, which claims an interest in the watershed, was not a party to the lawsuit.

In the latest court decision, attorneys for the poultry industry had objected to the state’s use of certain expert testimony.

The poultry industry has questioned both the methods and conclusions of several state-hired scientists.

Olsen has testified that poultry waste contains a unique combination of chemicals and bacterial components, a biological “signature” that he

Frizzell also excluded testimony from Valerie Harwood, a University of South Florida microbiologist who Edmondson claimed had isolated a biological fingerprint for the bacteria that would track to poultry.

The rulings this week were in line with Frizzell’s 2008 decision to reject the state’s request for a preliminary injunction to ban the use of poultry waste as fertilizer in the watershed.

In seeking the injunction, Edmondson claimed that use of poultry waste, called litter by the industry, as a fertilizer resulted in unacceptable levels of pathogens entering the watershed.

But Frizzell ruled that the state had failed to meet the applicable standard of showing that the bacteria levels in the Illinois River watershed could be traced to the application of poultry litter.

The judge noted that evidence showed that fecal bacteria in the watershed came from a number of sources, including cattle manure and human waste.

Charlie Price, spokesman for the Attorney General’s Office, said that “although we are disappointed that part of Harwood’s and Olsen’s testimony was excluded, neither is essential to our case. Our case remains intact and strong, and we look forward to presenting our evidence in September.”

The trial is scheduled to begin Sept. 21.