(Reuters) - A lawyer defending Las Vegas sports gambler William “Billy” Walters against insider trading charges on Wednesday sought to discredit former Dean Foods Chairman Tom Davis, who told jurors he used a special “bat phone” to give Walters confidential tips.

Lawyer Barry Berke’s cross-examination, which began on the fourth day of trial in Manhattan federal court, sought to undermine Davis’s testimony on topics including his own admitted history of marital infidelity and soliciting prostitutes.

Davis has pleaded guilty to insider trading charges and is cooperating with prosecutors.

Prosecutors say Walters was able to make more than $40 million thanks to tips from Davis, and that he passed insider information on to star golfer Phil Mickelson. Mickelson is not accused of wrongdoing.

Over the preceding two days, under direct examination by Assistant U.S. Attorney Brooke Cucinella, Davis told jurors that over a period of several years he gave Walters valuable information about Dean Foods, a leading dairy company, including advance notice of its earnings announcements and its plan to spin off part of its business in 2012.

Davis said Walters told him to use the code name “the Dallas Cowboys” for Dean Foods, and use a specially assigned phone, called the “bat phone,” to pass on information.

Under Berke’s cross-examination, Davis admitted that he was aware of no document in which the “Dallas Cowboys” code was used.

When Berke asked what color the bat phone was, Davis said it was maroon. But he conceded that he previously described it to prosecutors as black.

Berke also probed for inconsistencies in Davis’s testimony about his personal life. During direct examination, Davis had admitted that he had a history of infidelity in his first two marriages, and that he had paid for sex.

In response to Berke’s questioning, Davis confirmed he had told prosecutors he never paid for sex after marrying his third wife in 2007.

When Berke presented him with phone records showing later calls to escort services in several cities, he said he did not recall them, and that he did not pay for sex.

During the preceding two days of direct examination, Davis already admitted to stealing from a charity he helped run and committing tax fraud. He said Walters arranged loans for him when he was in financial distress, which he never fully repaid.

Davis also said Walters once recommended he invest in a company on the advice of billionaire investor Carl Icahn. Icahn has not been accused of wrongdoing.

The case is U.S. v. Davis et al, U.S. District Court, Southern District of New York, No. 16-cr-00338.