Casey Anthony Trial: Strong Forensic Evidence From Car But No Cause of Death

May 23, 2011 — -- When opening statements begin in Casey Anthony's murder trial Tuesday, what will Anthony's defense team be fighting for: exoneration or a guilty verdict that avoids the death penalty?

Anthony, 25, is accused of murdering her 2-year-old daughter Caylee Marie in 2008.

"It comes down to how the defense is going to define a win. If their goal is to have her completely exonerated, she would have to take the stand," said Richard Hornsby, an attorney who has blogged about the case which is scheduled to begin in earnest on Tuesday in an Orlando, Fla., courtroom.

"If their goal is a lesser manslaughter charge, I think it would be detrimental for her to testify because once she testifies and [if] the jury disbelieves her...she's testifying herself into the death penalty," Hornsby said.

Anthony faces a battery of charges including first degree murder, aggravated manslaughter of a child, aggravated child abuse and providing false information to law enforcement.

The most crucial piece of evidence for the prosecution is Anthony's 1998 Pontiac Sunfire. Forensic experts said the car's trunk tested positive for chloroform and decomposition.

"So much emanates from the car," said Jean Casarez, an attorney and legal correspondent for In Session on truTV. "Casey Anthony had possession and control of that car. She's the one that drove it. She's the one that ran it out of gas...From chloroform to the hair that had signs of decomposition, according to the prosecution, to the smell from the trunk of the car, to the doll in that car that Caylee Anthony loved."

No Strong Motive in Casey Anthony Murder Trial

Caylee Anthony was missing for a month when her grandmother Cindy Anthony called 911 in the summer of 2008 to report her granddaughter's disappearance. In the call, she was alarmed about her daughter's car.

"I can't find my granddaughter. There's something wrong. I found my daughter's car today and it smelled like there's been a dead body in the damn car," said Cindy Anthony in the July 2008 call to police.

Despite the car's forensic evidence, experts say the state doesn't have an air tight case against Anthony.

"There are so many pieces of strong evidence, but in a lot of them there seem to be strong evidence of reasonable doubt, too," Hornsby said.

There is no cause of death for Caylee. Her body was found in December 2008 by a meter reader near the home of George and Cindy Anthony, and was too decomposed to determine how she died. The little girl's death was ruled a homicide of undetermined means by the medical examiner.

"The first thing you need for premeditated murder is how she died. The motive for killing her is somewhat weak," Hornsby said.

In the 31 days while Caylee's disappearance went unreported, Casey Anthony was seen partying and getting a tattoo. Despite the damning impression that leaves, experts said that people who knew Anthony told investigators she was a good mom.

"The defense will say the way she reacted is more post-traumatic behavior. She reacted that way because she didn't know how to react to the death of her child and this is the only way she could cope," Hornsby said.

The prosecution will likely use Anthony's bizarre behavior in the month her daughter disappeared as evidence that Anthony was celebrating her daughter's death and newfound freedom, Hornsby said.

"What the defense is going to try to bring out, I believe, is that the elements of murder and committing a murder or having something horrible happen such as an accident must be separated away from those 31 days," Casarez said.

Casey Anthony May Use Alleged Abuse by Father in Defense

Anthony's parents, George and Cindy, will testify during the trial and Casey Anthony's relationship with them may even be part of her defense.

In jailhouse letters, Anthony told a fellow inmate that her brother, Lee, and father sexually abused her. Anthony's former boyfriend also has made the claim that her father sexually abused her. Using inmates as witnesses could be tricky for the prosecution.

"The prosecution has a lot of evidence and if they put at least one of these jailhouse snitches on the stand...that might allow the defense to cross examine the witness at that point and that brings allegations of abuse against Casey into the courtroom," said Casarez.

Anthony's defense lawyer Jose Baez repeatedly asked jurors during jury selection if they would consider someone for the death penalty who's been abused sexually. The issue of abuse will certainly come up during the sentencing phase of the trial.

"It appears where the defense is angling is it was an accidental death," Hornsby said. "One fork in the road is after they try to establish it was an accidental death."

Hornsby said the defense could pin Anthony's reluctance to come forward about her daughter's disappearance and death because of her fear of her parents and how they would react to her. That would likely not require her to testify, Hornsby said.

The start of the guilt phase of the trial on Tuesday follows 11 days of grueling jury selection and nearly three years of intense media scrutiny surrounding the case.

Judge Belvin Perry expects the eight week trial will draw more interest than the O.J. Simpson trial in 1994.

ABC News' Ashleigh Banfield contributed to this story.