A bug expert testified Friday that a key part of the prosecution's murder case against Florida mother Casey Anthony, the smell of death in the trunk of her car, can be explained instead as the smell of trash.

Anthony is accused of killing her 2-year-old daughter, Caylee, and dumping the body in the woods near their Orlando-area home. It was an eventful day of testimony Friday, with a wild scene outside the courtroom, as well, when some spectators got into a brawl.

The spectators -- many of whom arrive at the courthouse in the early morning -- line up outside the courthouse in hopes of securing one of roughly 60 seats in the courtroom.

The fight, which did not result in any arrests, erupted as the crowd was moving to a location closer to the courthouse entrance.

The Orlando Sentinel reported that two men tried to cut in line, starting a brawl and shouting match as others awaiting fought back.

In the courtroom, Anthony's attorney, Jose Baez, called Timothy Huntington, a forensic expert specializing in entomology, to the stand on Friday.

Huntington told jurors that he would have expected to have found hundreds of dead insects -- not only in the trunk but also in the passenger compartment of the vehicle if the child's body had been stored in the trunk.

Instead, he said, his analysis was consistent with the smell coming from a bag of trash with trash-feeding insects in it.

"There's nothing remarkable about that," Huntington said.

Huntington's testimony came on the second day defense witnesses have been called in the trial. Anthony is charged with first-degree murder in the death of her daughter, Caylee, in the summer of 2008. The toddler's skeletal remains were discovered in a wooded area not far from her grandparents' home that December.

Anthony has pleaded not guilty and faces a possible death sentence if convicted. The prosecution contends the child was suffocated by duct tape placed over her nose and mouth. The defense said in its opening statement that she drowned in her grandparents' swimming pool.

Huntington testified about the insects in the trunk of Anthony's car and at the scene where her daughter was found. The defense claims the smell from the trunk was from a bag of trash. Prosecutors say it came from the girl's body.

He said that what was observed at the scene where Caylee was found in terms of the types of insects and the volume of insects indicates that "the body was moved or transported from some other location to the site where it was discovered."

The defense's expert witness also testified about what he'd expect to see in the trunk of a car with a decomposing body, based on research about what happened to decomposing pigs inside car trunks.

In that research, which took place in September 2010 in Nebraska, Huntington put dead pigs in the trunks of cars and observed them as they decomposed. He referenced finding blow flies, or the first type of flies drawn to decomposing material, soon after death. He also noted the presence of a pronounced stain of decomposition fluid on the carpeting of the trunk.

He said he would expect to see the same things in a trunk with a decomposing human body.

"If we assume that a body was in the (Anthony) trunk, you expect to find many flies," Huntington said. "... I would expect to find hundreds, thousands of those dead insects as I did in the experiment."

Huntington described the decomposition fluid he observed in the pig experiment as distinct.

"It is a sticky, greasy, disgusting material," he said. "Once it soaks in there, I'm not sure a professional cleaner could get it out."

The morning also included a long period -- about 45 minutes -- in which the jury was sent outside the courtroom by Judge Belvin Perry while the attorneys argued over prosecutors' objection about whether Huntington was going to testify specifically about the stain its expert said was on the carpet in the Anthony car trunk.

Huntington reviewed reports made by prosecution bug expert Neal Haskell but never examined the trunk himself. Also, the pig research was conducted during September in Nebraska and not in Florida's hot summer months, when Caylee Anthony was reported missing.

Haskell testified last week that he found only a small number of bugs on the toddler's remains in the woods and on paper towels inside Casey Anthony's trunk. He also said that insects related to decomposition were found along with decomposition fluid on paper towels in the trunk.

Haskell estimated that the child's remains were inside the trunk for at least three days.

Huntington testified Friday that the only flies he found inside the trash bag taken from Anthony's trunk were those usually found in household garbage and not the ones attracted to the early stages of decomposition.

 Huntington testified about the insects in the trunk of Anthony's car and at the scene where her daughter was found.

The defense claims the smell from the trunk came from trash. Prosecutors say it came from the girl's body.

Anthony is charged with first-degree murder in the death of her daughter Caylee. She faces a death sentence if convicted. The prosecution contends the girl was suffocated with duct tape. The defense says she drowned in a swimming pool.

Caylee's skeletal remains were found in December 2008.

Click here to see video of the fight from MyFoxOrlando.com

TIMELINE: Casey Anthony murder trial 

The Associated Press contributed to this report.