Patrick McDermott, Olivia Newton-John's ex-boyfriend, volunteered to give a DNA sample to prove that he is alive.

After he and Newton-John brought their nine-year relationship to an end, McDermott disappeared in July 2005.

There were speculations that he faked his own death so that his son Chance could claim his life insurance.

He is believed to be staying near the Mexican resort of Puerto Vallarta on the Pacific coast using a new name, "Pat Kim".

Emails seen by the Herald Sun unveiled that private investigators want a saliva swab from Chance as this could help them verify the DNA sample that McDermott promised to send.

"Mr McDermott made it very clear that he has had no need for communication with anyone associated with her (Newton-John). He made that clear the day he broke up with her and through his counsel - his counsel says so," private investigator Phil Klein wrote in one of the emails.

Mr Klein was hired by a US TV network to look for McDermott. He has made contact with a man from Mexico who represents McDermott. However, Mc Dermott has never been sited nor has made any direct contact with him.

The US Coast Guard declared him lost at sea in 2005 when he disappeared during a fishing trip off California.