Prosecutors have DNA tests and hair samples. They have testimony about "the smell of death" in the trunk of the suspect's car.

What they do not have is a body.

Prosecutors building a case against a single 22-year-old Florida mother accused of killing her young daughter will have to rely on forensic evidence and convince a jury that Casey Anthony lacks credibility and had a motive, legal experts say.

To help build the case, the prosecutor will be using what he described as cutting-edge forensic tests, including air testing for compounds released when a body decomposes.

Prosecutors have not been specific about how the evidence led to charges against Anthony, but experts say it is possible to get a conviction without a body, with several cases, including some in Florida, as examples.

"Sometimes circumstantial evidence is as powerful, or more powerful than the body itself," said Donald Jones, a professor of criminal law at the University of Miami law school.

Since 3-year-old Caylee Anthony's disappearance was reported in July, investigators have taken air samples from her mother's car trunk and tested for the presence of her DNA. Hair samples also have been analyzed. The FBI and the Oak Ridge National Laboratory at the University of Tennessee performed the tests.

"The investigation contains intricate forensics that are on the cutting edge of science," said Lawson Lamar, State Attorney in Orange County.

It's not known how the forensics will play in court or for a jury.

Charles Rose, a law professor at Stetson University in DeLand, said the defense could contest the FBI findings of not being generally accepted. Also a lack of eyewitnesses and compelling physical evidence that directly links Caylee to a crime could be a problem.

"Any of us who've had a child for any amount of time know there's DNA evidence all over our cars," Rose said.

Still, the use of forensic evidence has an increased credibility with jurors because of what he calls "the CSI effect" from the CBS television series, Rose said.

"Right now, the belief is that the right cop with the right case can convict anything," Rose said.

In the air tests used on Anthony's trunk, air is run into a carbon compound filter, such as activated charcoal, which collects the evidence, said Arpad Vass, a research scientist at Oak Ridge. Air is then reversed through the filter, releasing the compounds.

In this case, they were looking for compounds released when a body decomposes.

"We essentially turn into the dust from which we come," Vass said. "We return to the compounds which break down and blow off into the air."

Donald Jones, a professor of criminal law at the University of Miami law school, said the air tests, though likely admissible, probably won't help make a connection the prosecution is seeking. He said the tests only reveal the presence of the compounds, not their source.

The Anthony case also has other pitfalls, law professors say.

The defense could emphasize a lack of motive and blame others who could have kidnapped or killed Caylee. Prosecutors would need to convince a jury why a mother would kill her child.

Besides first-degree murder, Anthony is charged with aggravated abuse of a child and aggravated manslaughter and with four counts of lying to investigators. Caylee was reported missing in July, but her mother told police she hadn't seen the girl since June.

A judge denied Anthony bond Wednesday. Dressed in a blue jail jumpsuit, Anthony made no comment during the minute-long hearing. Her attorney, Jose Baez, declined comment afterward. She will be arraigned in about a month. Continued...