LIVE STREAM: Testimony Resumes In Casey Anthony Trial - Watch It Here Live

On Wednesday, during a half-day session, the trial played out like an episode of CSI as a forensic expert for the defense cast doubt on the prosecution's star witness.

Chemist Michael Sigman from the National Center for Forensic Science testified that the car belonging to Anthony did not test positive for decomposition. Air samples from the Florida mom's trunk contained mainly gasoline, although chloroform and two other chemicals were present.

"I could not conclusively determine that the presence of those compounds indicated that there had been human remains in the trunk of that car," Sigman told jurors. He also said that chloroform is often found in bleach.

The prosecution has claimed that Anthony murdered her two-year-old daughter, Caylee and then hid the body in the trunk of her car.

While initial samples only showed up gasoline, Sigman told the jury that he did further tests that turned-up additional chemical compounds which are often found in cabbage, onions, bleach and spot removers.

A prosecution witness had previously said those compounds are also present in human decomposition but Dr. Sigman disagreed, telling the jury: "I can't say that decomposition occurred in that car.”

Dr. Arpad Vass testified earlier this month for the prosecution that the trunk of Casey's car had an abundance of chloroform, a sign of human decomposition and a chemical that also can be used to commit murder.

Earlier in the morning, the defense called a geologist to the stand who testified that no soil match was made between the site where Caylee's body was found and material found on Casey's shoes retrieved from her home.

The 25-year-old Orlando, Florida woman is accused of murdering her daughter after Caylee’s remains were found in woods near her family home in December, 2008.

Casey’s defense team maintain that Caylee drowned accidentally in the family swimming pool and that Casey’s father, George Anthony helped his daughter cover-up the death.