Gossip website RadarOnline has been posting several tapes of a man who sounds very much like Gibson, 54, in obscenity-laced tirades directed at a woman RadarOnline identifies as Grigorieva, a Russian singer.
Mel Gibson Demanding Sex Act in Latest Tape?
Mel Gibson Slur vs. Latinos Caught on Tape?
On Tape: Mel Gibson in Death Threat vs. Ex?
Mel Gibson's Thickening Legal Quandary
Can Mel Gibson's Career Survive Latest Ugliness?
Did Mel Gibson Beat Up His Ex?
They're in a bitter child custody battle, which moved inside a Los Angeles courtroom Thursday, though neither of them attended the session.
Their eight-month-old daughter, Lucia, is the subject of the dispute, but tapes apparently recorded by Grigorieva, 40, have been in the media spotlight.
The fifth such tape, another expletive-filled rant by the man alleged to be Gibson, has him claiming he's spent $5 million on Grigorieva and calling her a gold-digger.
But, as CBS News Correspondent Ben Tracy reports, the Oscar-winner's lawyers assert the tapes have been edited, and at least one forensics expert agrees.
During the closed court session, Tracy says, attorneys for Grigorieva contended phone calls like the ones in the recordings are the reason Gibson can't be trusted.
In the latest, the man is heard saying, "I like to show you what mean really is, b**ch, c**t, whore, gold-digger. All true. You f***ing proved it to me."
The L.A. Sheriff's Department is investigating Gibson for domestic violence. Grigorieva has accused him of hitting her and waving a gun in her face.
Authorities received tapes from the court Thursday, though no one was saying whether the tapes they got included the ones RadarOnline posted.
"We will secure them, book them in to evidence," Steve Whitmore, of the Los Angeles County Sheriff's Department, told CBS News. "We will then begin the process of reviewing them, analyzing them."
But Gibson's lawyers allege that the phone calls have been edited, and forensic expert Frank Piazza says they have a point.
One he pointed to "definitely has edits, deliberate edits," Piazza told CBS News.
Gibson, an Oscar-winner once reportedly worth close to $1 billion, now says he's in a financial bind, Tracy says, and blames Grigorieva and her failed music career, which he helped bankroll.
At least, the man on the tape does. He says, "I spent too much G*d-damn money on you, and my wife knows," the man says. The woman says, "How much money do you spend on me? You don't spend more money on me than anybody else." The man replies, "I spent more than 5 million dollars on you!"
Gibson has eight children, seven with his wife of 28 years, Robin, who is expected to get a huge divorce settlement. In a letter to the court, Robin Gibson says Gibson never abused her and was a good father.
But, says Tracy, the words of the man on the tape may prove hard to explain, words such as, "I will never forgive you for what you've done to me. You f -- ing b-tch!"
The increasingly nasty custody battle is slated to continue in court next week.
CBS News legal analyst Lisa Bloom says the impact of the tape could be "huge," even if they were edited, and comments on a late report by celebrity website that Grigorieva demanded $10 million in hush money from Gibson to keep from going public with the tapes. Bloom says such reports are common in high-profile cases like this one: