Beverly Hills billionaire Kirk Kerkorian took the stand Wednesday in the high-profile wiretapping conspiracy case against his longtime attorney Terry Christensen and private sleuth Anthony Pellicano.

Wearing a navy sports jacket and gray slacks, 91-year old Kerkorian made a rare public appearance for Wednesday’s testimony. A man held Kerkorian’s arm to steady him as he slowly entered the Los Angeles federal courtroom, where he was on the stand for about 30 minutes.

Kerkorian was asked to testify about his knowledge of wiretapping in his paternity battle with ex-wife, Lisa Bonder Kerkorian. He was questioned by both Assistant U.S. Attorney Kevin Lally and attorney Patricia Glaser, who is defending Christensen, her law firm partner.

Kerkorian testified that he no knowledge of wiretapping in the dispute.

And when asked about Christensen, Kerkorian described the attorney as “excellent, honest, straightforward and a true friend.”

Kerkorian, chief executive of Tracinda Corp., is the most prominent person to testify thus far in the case. The Business Journal estimated his wealth at $10.6 billion in May, making him L.A.’s wealthiest resident.

Christensen has been accused by prosecutors of hiring Pellicano to illegally wiretap Bonder Kerkorian to help Kerkorian in a dispute over child support. Bonder Kerkorian was asking Kirk Kerkorian for $320,000 a month in support, but DNA tests later showed that movie producer Steve Bing was the father.

Earlier this year, Pellicano was convicted of illegal wiretapping and racketeering in a separate case but faces new charges in this one.

Kerkorian was called to testify today by Christensen’s defense attorneys, who have denied that their client had any knowledge that Pellicano was conducting wiretaps. They contend that the private investigator was paid $100,000 because Bonder Kerkorian was threatening to harm Kerkorian and her own child.

Kerkorian appeared alert, although he asked Glaser and Lally to repeat their questions several times.