Building a Case Against Drew Peterson

May 11, 2009 — -- As Drew Peterson sits in jail on murder charges for his third wife's death, his stepbrother could prove key to the prosecution's case that he also killed his still-missing fourth wife, Stacy Peterson.

Drew Peterson is being held now only for the 2004 murder of Kathleen Savio, whose death the medical examiner had initially ruled a drowning accident. But a grand jury is still hearing evidence that alleges Peterson's involvement in Stacy Peterson's death.

Included in that evidence are statements from Thomas Morphey that 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?'"

Neither Stacy Peterson nor her body have ever been found, nor has the mysterious blue barrel.

While the allegations against Peterson and his seemingly blase attitude toward the fate of his two wives have made him an unpopular media figure, prosecutors face the burden of convincing a jury he's guilty using evidence that's reportedly circumstantial at this point.

Prosectors 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."

Prosecutors are banking on a new Illinois state law that would essentially allow Savio's words to be heard from the grave. But the law allows such statements only if the witness was killed to prevent him or her from testifying.

"These statements are not subject to cross examination," legal analyst Dana Cole told "Good Morning America," "and under current U.S. Supreme Court rulings if a statement is not subject to cross examination it's hearsay and may be inadmissible."

Peterson's lawyer, Joel Brodsky, has said he'll challenge the law as unconstitutional.

Brodsky has called the $20 million bond "excessive" and said he hoped to get it reduced. Another attorney told The Associated Press that Peterson had an alibi for Savio's death.

The defense also plans to play up the results of Savio's first autopsy that ruled her death in the bathtub an accidental drowning. The second autopsy, done after Stacy Peterson disappeared in 2007, ruled Savio's death a homicide.

If a murder indictment is handed down in Stacy Peterson's death, 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," Cole said.