A string of expert witnesses took the witness stand on Wednesday, the 25th day of Casey Anthony's trial, but none of their testimony could prove that Casey had killed her 2-year-old daughter Caylee.

Michael Sigman, a chemistry professor at the University of Central Florida who formerly worked with the prosecutor's witness Dr. Arpad Vass, testified that although gasoline, chloroform, and other chemicals were found in the air sample taken from Casey's car, he can't confirm that Caylee's corpse was in the trunk of Casey's car.

Based on our data, I cannot say there were human remains in that trunk, said Michael Sigman. He also said though he detected an odor in the car, he couldn't say for sure that it smelled of decomposition.

Prosecutor Jeff Ashton said the air sample, which was taken from the trunk of Casey's car after the trunk's carpet liner and spare tire cover had been removed, isn't credible. And the methods, which Sigman used to study, were not as authoritative as Vass' method, he said.

Maureen Bottrell, an FBI forensic examiner and an expert in geology, testified that the soil in Casey's shoes didn't match with the soil at the remains site.

Bottrell had analyzed 22 pairs of Casey's shoes, which she acquired in 2009, a bag containing those shoes, and a shovel, which Casey had borrowed from her neighbor, debris from the trunk of Casey's car, and soil samples from the place where Caylee's body was found.

Bottrell said she could not scientifically relate Casey's shoes with the remains site. During cross-examination, she also acknowledged that even there's no soil evidence to prove that Casey was at the remains site, it doesn't exclude the possibility as the soil can be easily removed or mixed with soil from another place.

Another FBI expert in toxicology, Madeline Montgomery, gave her testimony in the court on Wednesday. She studied Caylee's hair among the remains and found 11 traces of drugs including sedatives. Under cross-examination, she affirmed that hair was not the best way to test for drug exposure.

An FBI forensic chemist, Michael Rickenbach, also testified that he tested items such as Caylee's car seat, Casey's steering wheel cover, a doll found in the car, a Gatorade bottle and a World of Disney shopping bag and testified he didn't find chloroform.

Karen Lowe, another FBI forensics expert, was the final witness on Wednesday. Lowe analyzed the hair sample from the trunk liner for decomposition and compared duct tapes in the crime scene and Anthonys' home. The result proved no evidence for decomposition.

Lowe also said that the duct tapes found at the remains site and Anthonys' home had a different fabric make-up though they shared the same brand.

Wednesday's court proceedings finished earlier than normal as Judge Belvin Perry had a prior commitment. The trial will resume on Thursday morning and will make up the missed half of Wednesday on Saturday.

About Casey Anthony Trial

Two-year old Caylee was last seen alive on June 16 and it was only on July 15 that she was reported missing by her mother Casey Anthony to the police. Cindy, Casey's mother had also alerted the police by calling a 911 dispatcher and saying that she had smelled a dead body in the trunk of Casey's car that was spotted in an impound lot. The car was later towed by authorities for forensic analysis.

Initially, Casey told the police that a babysitter called Zenaida Fernandez-Gonzalez (Zanny the nanny) had abducted Caylee. Investigations showed Casey was lying as the babysitter Zanny was fictitious. Five months later, in December 2008, Caylee's decomposed skeletal remains were found in a wooded area near the Anthony home by a meter reader who was relieving himself.

The prosecutors say Casey chloroformed Caylee and then put duct tape over her nose and mouth, suffocating the girl.

Casey's lawyers claim Caylee was not murdered. They say the toddler accidentally drowned in the family swimming pool and George, Casey's father, helped her keep the death a secret. George has denied the claim.

Casey has been charged with seven counts, including first degree murder, aggravated child abuse and misleading the police in the death of Caylee. If she is convicted of first degree, she could be sentenced to death by the seven-woman, five-man jury. The trial is expected to take another 2-3 weeks before a verdict is reached.

Must Read: Casey Anthony Trial Day 22: Forensic expert testimony makes Judge Perry livid

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