The latest twist in the drew peterson trial. The former police officer accused of killing his wife. The defense resting without calling him to the stand. But he did get a strong show of support from... See More
The latest twist in the drew peterson trial. The former police officer accused of killing his wife. The defense resting without calling him to the stand. But he did get a strong show of support from another key witness, his son. Abc's linsey davis has the story. Reporter: Just before the defense rested its case wednesday, drew peterson, the man accused of murdering his third wife, kathleen savio, told the judge he wouldn't be taking the witness stand. But his 19-year-old son did. The defense called thomas peterson as its final witness. He was just 11 years old in 2004 when his mother was found dead in her bathtub. I believe that my dad is innocent, he said. And when asked to recall the night peterson told him and his brother their mother had died, thomas told the court his father was very, very shaken up about it. I had never seen anyone so sad. Peterson, a former chicago po officer, says the first-degree murder charges against him are bogus. His attorneys say savio drowned in a bathtub after slipping and hitting her head. Her death was initially ruled an accident and wasn't reclassified as a homicide until his fourth wife, stacy peterson, disappeared in 2007. I don't know. Reporter: Before she vanished, stacy peterson allegedly told a divorce lawyer she believed her husband was guilty of murder. The defense called that lawyer to the stand wednesday, hoping he'd establish that her claim was simply made up, in an attempt to extort money from peterson. But their plan backfired. Harry smith told the court, she wanted to know if, in my opinion, if the fact that he killed kathy could be used against him in the divorce proceedings. Three squares. How can I beat that? It backfired completely. That will be probably the main thing that leads to his conviction. Reporter: The defense immediately went into damage-control mode. Calling smith a hostile witness and accusing him of perjury. Earlier in the week, two doctors testified savio's death was consistent with an accidental death. A stark contrast from a witness for the prosecution last week who sa the tub's edges weren't pronounced enough to cause the kind of wounds savio had on her head. This morning, the state has its rebuttal case. Closing arguments are expected on tuesday. Linsey, thank you very much.
This transcript has been automatically generated and may not be 100% accurate.