Creative Forensic Services chief Arlo West, who has worked on a number of high profile crimes in the United States, says the recordings are of "extraordinary" quality and appear to have been made using a professional-standard microphone. Mel Gibson ... tapes allegedly tampered with, experts believe. "In the tapes themselves there are several things that would raise a red flag as an expert," Mr West told Good Morning America. "I found gaps, transients and fades. All three of these things would be considered in authenticating the audio itself." Gibson and Grigorieva are locked in a bitter legal battle over custody of their eight-month-old daughter, Lucia.

The series of recordings were leaked during the past week to celebrity gossip website RadarOnline.com. Before the split ... Robyn and Mel Gibson. They allegedly feature the Oscar-winning Braveheart director using racist language to disparage a Hispanic cleaning lady. In earlier tapes Gibson referred to black people as "niggers," called Grigorieva a "whore" and a "bitch in heat", and apparently acknowledged beating her. While they have not been authenticated, Gibson has not issued any denial since they began surfacing on Friday.

But website TMZ reports that his lawyers are preparing to present evidence that the tapes have been tampered with. Mel never engaged in any physical abuse of any kind toward me before, during or after our marriage.Mel was a wonderful and loving father A second expert, Frank Piazza, who worked on the Jon Benet Ramsey murder case 14 years ago, supported Mr West's assertion. "There are redactions, things were taken out, there were obviously things people didn't want others to hear," Mr Piazza told HollywoodLife.com. Detectives investigating Gibson for the possible domestic violence case say they have received audio recordings from a court deciding the actor-director's child custody case.

Sheriff's spokesman Steve Whitmore said the CDs were turned over during a closed session in the custody case. The speculation comes as Gibson's soon-to-be ex-wife Robyn reportedly filed a declaration in support of the star. Robyn Gibson said in the document her husband of 28 years had never physically abused her or any of their children, TMZ.com reported. "Mel never engaged in any physical abuse of any kind toward me before, during or after our marriage," the one-page declaration states. She adds: "Mel was a wonderful and loving father."

Sheriff's spokesman Whitmore said detectives were working to authenticate the recordings released by the court. He did not say how many recordings were included or how long they were. It is unclear whether the recordings include those that have been posted by the celebrity website RadarOnline.com. The site has posted more than 20 minutes of recordings of arguments between a man who sounds distinctly like Gibson and a woman identified by the site as Grigorieva. Whitmore said detectives still hoped to speak to Gibson, who has not yet been interviewed.

Detectives are looking into allegations that Gibson harmed Grigorieva during a January confrontation. He said he would not speculate on when the case would be turned over to prosecutors, who will decide whether Gibson should face criminal charges. Loading "It's not going to be rushed," Whitmore said. - with agencies.