Two representatives for Williams Companies Inc. were questioned by prosecutors on Wednesday about a donation the Tulsa, Okla., energy company made to DeLay's political action committee.
The testimony comes as some question the strength of the prosecution's case.
DeLay is accused of using his PAC to illegally funnel corporate donations to Texas GOP candidates in 2002. Prosecutors say further evidence will tie DeLay directly to the alleged scheme.
DeLay denies wrongdoing. The former Houston-area congressman is charged with money laundering and conspiracy to commit money laundering.