Peterson's sons to testify before grand jury

null ABC News has learned Peterson's sons with his third wife, Kathleen Savio, have been granted immunity, so they have to testify.

Peterson is a suspect in the disappearance of his fourth wife, Stacy. That case prompted investigators to exhume Savio's body for a new autopsy.

Savio's death was ruled a homicide last week. Four years ago, a coroner's jury ruled it was an accident.

ABC News spoke to a member of that 2004 jury.

"I look back and I think if we would've came back with murder rather than accidental death, not saying that Drew Peterson would've been charged with it. But if we would've came back with murder instead that maybe Stacy Peterson would be here today," said Jim Pretto, former coroner's jury member.

And you can hear more from that interview with Jim Pretto later on Good Morning America.

Copyright © 2019 WLS-TV. All Rights Reserved.