Casey Anthony’s lawyers again called witnesses to dispute forensic evidence as trial proceedings got underway on Wednesday. Yesterday, Dr. Jane Bock, a forensic botanist, offered potential holes in the state’s timeline; today, Michael Sigman, a chemist at the National Center for Forensic Science, testified about air samples in the trunk of Anthony’s car.
Air samples from the trunk, and methods testing for evidence of human decomposition, have been among the most contentious evidence yet in the 25-day trial. One of the prosecution’s most compelling witnesses was Dr. Arpad Vass, a forensic anthropologist at the Oak Ridge National Laboratory in Tennessee. Vass told jurors about odor analysis techniques he developed at University of Tennessee’s “body farm,” where he created a database of 400 chemical vapors present in human decomposition.
While Vass’s testimony appeared airtight, many forensic scientists question whether it should have been admitted under Florida’s Frye statutes. “It’s what the state calls ‘state of the art.’ It’s what I call ‘not ready for prime time,'” Dr. Lawrence Kobilinsky, head of the Forensic Sciences Department at the John Jay College of Criminal Justice, told TIME. “It’s not junk science, but it never should be brought into a courtroom at this stage.”
But Jose Baez, Anthony’s lead attorney, appears to be taking no chances with a possible appeal if his client is convicted. Sigman testified today that chloroform was present in the trunk, but that the most abundant vapor was gasoline. “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 said, directly contradicting Vass’s earlier testimony.
On cross examination, Sigman admitted that his methodologies were not as good as those Vass used. Sigman used bags to capture air samples, while Vass used a “triple sorbent trap.” Earlier in the trial, Vass told jurors that the trunk had a powerful odor of death. Today, prosecutors asked Sigman whether the trunk smelled like it contained a dead body. He admitted that it did smell, but said that he doesn’t study human decomposition and could not definitively place the smell.
Defense witnesses have, so far, provided plausible alternatives to the state’s forensic evidence, but Baez has yet to provide any evidence to back up the allegations made in his opening statement that Casey’s father, George, disposed of 2-year-old Caylee’s body after the toddler accidentally drowned. Technically, Baez has to prove nothing for Casey to be acquitted; the prosecution must prove beyond a reasonable doubt that Casey committed the crime. But such a bombshell explanation at the trial’s outset with no follow up probably won’t sit well with jurors who have now heard dozens of days of dense, scientific testimony. Baez must soon choose whether to put Casey on the stand. If he does, it’ll be something to watch.
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