ORLANDO, Fla. — An expert in human decomposition testified on Monday that air and fiber samples from Casey Anthony's car trunk contained chemical compounds emitted by decaying human remains.
Arpad Vass of the Oak Ridge National Laboratory in Tennessee said the test results confirmed what his nose had already told him.
"The odor was extremely overwhelming ... I recognized it as human decomposition," said Vass, a pioneer in the biochemistry of human decomposition.
Casey Anthony, 25, is standing trial for a first-degree murder charge stemming from the June 16, 2008, death of her 2-year-old daughter Caylee.
Prosecutors are trying to prove that Anthony suffocated her daughter with duct tape and contend that traces of decomposition were found in her car.
Anthony has pleaded not guilty. Her defense attorney says the toddler drowned in her grandparents' swimming pool. If convicted, the 25-year-old Anthony could be sentenced to death.
Legal experts say the air analysis could be used as grounds for an appeal if Casey is convicted.
Defense lawyer Jose Baez objected repeatedly to Vass' testimony on Monday. He argued Vass was testifying out of his field of expertise or about lab work performed by another scientist at Oak Ridge.
At one point, Baez questioned Vass out of the jury's presence so the trial judge could hear what questions the defense attorney wanted to ask.
During that exchange, Vass told Baez, "I don't think you quite understand what's happening here."
Vass testified that he has worked for 20 years in the Oak Ridge lab's outdoor body farm, where human remains are studied in various stages of decomposition. He said he has worked with 50 bodies from the time of death until they were skeletonized, plus hundreds of other bodies in various stages of decay.
In the air analysis of the car trunk sample, Vass said he and other scientists detected 51 compounds including an unusual quantity of chloroform. Chloroform is released by decaying bodies, Vass testified.
"We were shocked. We had never seen chloroform at that level," Vass testified.
In their opening statement, prosecutors told jurors someone had researched chloroform, once a popular anesthetic, on the Anthony family computer in the months before Caylee's death.
Vass testified the lab also conducted laser tests on a sample of the carpet from Casey's car trunk to look for inorganic elements such as calcium, sodium, magnesium, iron and carbon. Vass said calcium was found in the greatest quantity.
"They showed the inorganic elements associated with human decomposition were significantly elevated," Vass said.
Further chemical tests of the carpet were performed to look for compounds that had not been converted to a gas but were stuck in the fibers. Vass said the tests uncovered butyric acid.
"It is the first (fatty acid) compound liberated during human decomposition," Vass said.
Vass said all the results were compared to tests of samples of carpet from the trunks of two cars pulled from a junkyard in Knoxville which showed no significant levels of any of the compounds or elements.
Judge Belvin Perry previously issued a pretrial order denying a defense request to exclude the air tests.
Until now, the tests had never been admitted in a trial in the United States.
Setting the stage for Vass' testimony, Orange County Sheriff's Office crime scene supervisor Michael Vincent testified on Saturday that he helped obtain several air samples from the car trunk and a forensics bay where the sheriff's office stored the car.
Vincent said air samples also were taken from a bag of trash that had been in the car trunk.
The samples were sent to Vass. The Oak Ridge lab deems his work "groundbreaking," but defense lawyer Jose Baez has dismissed it as "junk science."
Over the weekend, the jury heard that a single 9-inch-long brown hair found in Anthony's car trunk could have been ripped from the dead body of her daughter.
'Consistent with apparent decomposition'
Karen Korsberg Lowe, who specializes in microscopic examination of hair samples at the FBI Laboratory in Quantico, Va., testified she found "root-banding" on the hair, something she said scientists have never seen other than on hairs from decomposing bodies.
"It has darkened bands at the root portion ... . This is consistent with apparent decomposition," Lowe testified. Shealso testified the hair appeared under a microscope to be similar to one recovered from Caylee's hairbrush.
The hair evidence, which an FBI expert testified about on Saturday, is among the most contentious in the case. Baez contends the science behind some of the hair analysis is new and unreliable.
Prosecutors contend Anthony killed her daughter on June 16, 2008, and dumped her body in woods near the Anthony home.
Baez has told jurors Caylee drowned accidentally in the backyard pool but that her death went unreported.
Caylee was first reported missing July 15, 2008, by her grandmother Cindy Anthony after finding Casey's car at an impound lot. Cindy and a series of witnesses have testified that the car was permeated by a strong stench that they likened to the odor of a body.
Casey told detectives Caylee was kidnapped by a nanny. But after a nationwide search, Caylee's skeletal remains were found in December 2008 in woods a 10-minute walk from the Anthony family home.
Reuters and The Associated Press contributed to this report.