Scott Peterson's lawyer is battling an important prosecution theory.
As he wrapped up his closing arguments Wednesday, Mark Geragos told the jury there's little evidence to prove whether or not Laci Peterson's fetus died before or after birth.
Geragos says if the fetus died later, "It's not Scott Peterson who did that."
The defense has argued that the fetus was born alive, perhaps providing an alibi, because police were already following Scott Peterson around the time the baby was due.
A defense witness has testified the baby could have been born weeks after Laci Peterson vanished.
Now that the defense has wrapped up its case, a prosecution rebuttal will follow this afternoon.
The jury in Redwood City, California, then gets the case.