By Jennifer Greenhill-Taylor
ORLANDO, Fla (Reuters) - A forensic toxicologist testified on Thursday that tests done by prosecution experts on air samples from Casey Anthony's car trunk were marred by errors and departures from correct procedures.
Casey, 25, is standing trial in Florida for a first-degree murder charge, accused by prosecutors of using duct tape to suffocate her 2-year-old daughter Caylee on June 16, 2008 and then storing the child's body in the trunk of her car.
Arpad Vass, a scientist at the Oak Ridge National Laboratory and a pioneer in the biochemistry of human decomposition, testified earlier for the prosecution on his analysis of air from the trunk. He concluded that a body likely had been there.
But testifying for the defense in the fifth week of the trial, analytical chemist and forensic toxicologist Barry Logan said a research lab like Oak Ridge did not have to adhere to the same stringent protocols as a forensic lab because their missions were different.
A forensic lab tested samples for law enforcement or legal review, while a research lab's mission is to discover new things, Logan said.
Prosecutors are seeking the death penalty against Casey. Their introduction of the air tests is novel scientific evidence that the defense team has challenged.
Defense attorneys maintain Caylee drowned in the family's backyard pool. Her skeletal remains were found in woods near the Anthony family's home in the Orlando area on December 11, 2008, following a nationwide search.
As the defense continued to try to chip away at the prosecution's case, testimony on Thursday focused on tests and methods used to identify chemicals in air and hair.
Witnesses got little time to actually testify on their fields of expertise, as numerous objections from the prosecution, along with extended meetings between the attorneys and judge at the bench, took up much of the morning.
Stephen Shaw, a hair and fiber examiner with the FBI who testified for the prosecution earlier in the month, took the stand again to discuss the science of post-mortem hair banding.
He had analyzed hairs from Casey's trunk and from the hair mass found with Caylee's skull. Dozens of slides of hairs from living people and cadavers were again shown to jurors as the defense tried to undermine the effectiveness of the technique used to identify hair from a dead body.
"The science as it stands can't tell whether a hair comes from a living or dead person," defense attorney Jose Baez said to Shaw.
"That's true," Shaw said.
Still more slides were shown during prosecutor Jeff Ashton's cross examination, as he attempted to assure jurors that experts could indeed identify hair from a dead body through the microscopic identification of specific dark areas on the hair.
(Editing by Colleen Jenkins and Greg McCune)