If a murder indictment is handed down for the Stacy Peterson case, experts said it could vastly change the case against Drew Peterson.
"Then I think the prosecution will combine both cases, and each case will sort of feed off the other and will present a powerful picture to both a trial judge and a jury that this guy is a serial murderer," legal analyst Dana Cole told ABC's "Good Morning America" last week.
Peterson told "Today" that he will "probably be found innocent" of Savio's murder. He has also repeatedly said he had nothing to do with Stacy Peterson's disappearance.
Joel Brodsky, has said he will ask to have Peterson's bond reduced. He has also said he expects to challenge a new Illinois state law that could prove vital to the prosecution's case.
Prosecutors are hoping they can enter into evidence writings from Savio when she was in the midst of her divorce from Peterson, that she feared her husband's "next step is to take my children away or kill me."
A new Illinois state law allows such statements only if the witness was killed to prevent him or her from testifying.
In the Stacy Peterson case, testimony from Thomas Morphey, Peterson's stepbrother, could be damaging. Morphey says he helped his stepbrother move a large blue barrel from Peterson's home on the last day Stacy Peterson was seen alive.
The day before he helped move the barrel, Morphey said Peterson confronted him. "He said, 'How much do you love me?'" Morphey told "Good Morning America" in March. "I said, 'I do.' And he said, 'Enough to kill for me?'"
Stacy Peterson has never been found, nor has the mysterious blue barrel.
Morphey was seen last week entering the Will County Court Annex Building, where the grand jury has been meeting for 18 months, according to the Chicago Tribune. The grand jury's term expires May 21. If the grand jury does not return an indictment, the investigation could continue with another panel.
Stacy Peterson's friends and family said after Peterson's arrest that seeing Peterson in handcuffs is bittersweet.
"It's a very hollow victory right now not knowing where Stacy is," said Sharon Bychowski, a friend of Stacy Peterson who lives next door to Drew Peterson. "We still have a ways to go. It wasn't quite the victory I thought it would be."
Pam Bosco, a friend and family spokesman, said the family "understands that it's ongoing and we just have to be patient with it."
The Associated Press contributed to this report.