Phil Mickelson one of 20 on defense's witness list for Billy Walters trial

Phil Mickelson is on the witness list for the defense in the ongoing insider trading trial of Las Vegas businessman and renowned sports bettor William "Billy" Walters, but it is not known whether the professional golfer will take the stand as the trial heads into its second week in New York.

Walters is charged with conspiracy and securities fraud, stemming from a series of stock trades made in 2012 involving Dallas-based dairy company Dean Foods. The government alleges that Walters received inside information from former Dean Foods executive Thomas Davis and passed tips along to friends, including Mickelson. Davis, according to a court documents, is a cooperating witness for the government.

Walters has denied any wrongdoing.

Mickelson is listed as the 13th witness on the defense's 20-person list. He is not on the government's witness list.

A spokesman for Mickelson declined comment regarding the trial and witness list when reached by ESPN on Saturday. Walters and Mickelson are longtime acquaintances, often playing golf together in the past.

Mickelson did not play in this weekend's Arnold Palmer Invitational but is tentatively scheduled to play in the WGC-Match Play starting Wednesday in Austin, Texas.

During the first week of the trial, when Judge Kevin Castel asked the prosecution if Mickelson would testify, Assistant U.S. Attorney Daniel Goldman said he "will be part of this trial," according to Bloomberg.

Barry Berke, Walters' attorney, argued in his opening statements that relaying any information to a high-profile celebrity such as Mickelson would be the last thing someone would do in any alleged insider trading scenario.

"If you're Bill Walters and somebody's giving you inside information, the last thing you would do is give it to Phil Mickelson, one of the most famous athletes in the world, who is going to attract regulatory scrutiny," Berke told jurors.

The Securities and Exchange Commission accused Mickelson of using a tip from Walters to make $931,000 on a trade involving Dean Foods in 2012. Mickelson was not criminally charged, but in May 2016, he agreed to pay back "all ill-gotten gains," which, with interest, totaled $1.03 million.

A spokesman for Mickelson at the time said the golfer had "no desire to benefit from any transaction that the SEC sees as questionable."

"Phil understands and deeply respects the high professional and ethical standards that the companies he represents expect of their employees, associates and of Phil himself," the statement said. "He subscribes to the same values and regrets any appearance that, on this occasion, fell short. He takes full responsibility for the decisions and associations that led him to becoming part of the investigation.

"... He is pleased that this matter is over, and he will have no further comment."