Relatives of Rebecca Zahau don't accept the medical examiner's conclusion that she committed suicide in July at the Coronado home.
As a result, a pathologist on the East Coast will conduct another autopsy as early as Friday.
Zahau's naked and bound body was found at the mansion owned by her boyfriend, Scottsdale, Ariz., pharmaceutical executive Jonah Shacknai.
Authorities say Zahau killed herself because she was distraught over the death of Shacknai's son, Max.
The 6-year-old boy died from injuries he sustained during a fall two days earlier.
Shacknai is founder and chief executive of Medicis Pharmaceuticals Corp. and owner of the 27-room waterfront mansion. Zahau was his girlfriend of two years. Max was his son from a marriage that ended in divorce.
The Associated Press contributed to this story.