By Barbara Liston
ORLANDO, Fla (Reuters) - 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 in Orlando, Florida for a first-degree murder charge stemming from the June 16, 2008 death of her 2-year-old daughter Caylee.
Prosecutors are seeking the death penalty. Monday marked the start of the third week of the trial.
Prosecutors contend Casey hid her daughter's disappearance for a month until her parents, Cindy and George Anthony, found Casey's car at an impound lot on July 15, 2008, suffused with what they recognized as the smell of death.
When Casey refused to let her mother see Caylee, Cindy called 911 and reported the child missing.
Defense lawyer Jose Baez claims Caylee drowned accidentally in the family's backyard pool. He fought without success to ban Vass's testimony before trial, calling the science new and unreliable.
Legal experts say the air analysis could be used as grounds for an appeal if Casey is convicted.
Baez objected repeatedly to Vass's 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.
Vass said his research determined the chemical compounds emitted by human remains at various stages of decomposition.
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.
Vass's testimony was expected to continue Monday afternoon.
(Editing by Colleen Jenkins and Jerry Norton)