VIDEO: Casey Anthony Must Take The Stand, Expert Says

Two former roommates of Casey Anthony's boyfriend testified Wednesday that the mother accused of killing her 2-year-old daughter never appeared worried, depressed or angry even though her toddler had disappeared.

Casey Anthony listens during the first day of her murder trial at the Orange County Courthouse on Tuesday, May 24, 2011. Anthony is on trial for the murder of her 2-year-old daughter. (AP Photo/Red Huber, Pool)

ORLANDO, Fla. — Two former roommates of Casey Anthony's boyfriend testified Wednesday that the mother accused of killing her 2-year-old daughter never appeared worried, depressed or angry even though her toddler had disappeared.

The ex-roommates, Cameron Campana and Nathan Lezniewicz, said they met Caylee in early June 2008, but the girl eventually stopped coming to the apartment. When they asked Anthony about the toddler, both men testified that she told them the child was with her nanny.

Anthony, 25, is charged with first-degree murder in the death of her daughter. If convicted, she could be sentenced to death. She has pleaded not guilty.

The trial began Tuesday with explosive allegations and two very different theories about how the little girl died.

For the first time, prosecutors said Caylee died from three pieces of duct tape being placed over her mouth and nose. Anthony's attorney claimed the toddler drowned in the family pool and the toddler's grandfather helped cover up the accident. The attorney, Jose Baez, also leveled accusations that Anthony was sexually abused by her father, an allegation he disputed when he took the stand Tuesday as the first witness in his daughter's trial.

The contrasting explanations about how Caylee died were offered to the jury in part because an autopsy was never able to conclude a cause of death. Prosecutors believe they have enough circumstantial evidence to prove Casey killed her daughter during the summer of 2008.

Anthony waited a month before telling her mother Caylee had disappeared, and that was only after her parents, George and Cindy Anthony, had recovered a foul-smelling car Casey Anthony had been driving, prosecutors said. The vehicle was picked up from a towing lot.

During the month Caylee was missing, Casey Anthony went shopping, visited friends and hung out with her boyfriend. Between each description of how Casey Anthony spent her time, prosecutor Linda Drane Burdick told jurors: "Where is Caylee Marie Anthony?"

Defense attorney Jose Baez presents his arguments during opening statements for the Casey Anthony murder trial at the Orange County Courthouse, Tuesday, May 24, 2011 in Orlando, Fla. Anthony is charged with killing her 2-year-old daughter Caylee in 2008. (AP Photo/Red Huber, Pool)

She was living with her boyfriend's ex-roommates at the time. Campana is a club promoter in Cleveland who was attending Full Sail University in Orlando in 2008 and Lezniewicz is in a band and also attended Full Sail University.

Prosecutors said everything Casey Anthony did was based on a web of lies.

"Casey Anthony ... appeared to be ... a loving mother, trying to provide support for her daughter," Burdick said. "But as the evidence in this case will show, that was an illusion."

Baez, the defense attorney, laid out a laundry list of accusations to explain Casey Anthony's behavior, including that George Anthony molested his daughter, that her brother, Lee, also made advances toward her and was given a paternity test to see if he was Caylee's father. All those secrets eventually led to the cover up of Caylee's drowning, Baez said.

"You will hear about a family that is dysfunctional," Baez said. "Ugly things. Secret things."

Baez went even further, saying George Anthony planted duct tape matching the brand later found over Caylee's mouth in a way that would implicate his daughter.

"George Anthony took certain steps to make sure he was as far away from this situation and that Casey would end up taking the blame for this," Baez said.

George Anthony told jurors Caylee didn't die at his house, and he denied disposing of her body and placing duct tape over her face.

"I would have done everything possible to save my granddaughter if what was said happened, happened," he said.

Baez also picked at prosecution assertions that the odor emanating from Casey Anthony's car was caused by a decaying body. It was actually from a bag of garbage that had been left in the trunk, he said.

"Reasonable doubt is not sprinkled through this case," Baez said. "Reasonable doubt lives here."

Casey Anthony reacts in court during her trial at the Orange County Courthouse, Tuesday, May 24, 2011, in Orlando, Fla. Anthony is charged with killing her 2-year-old daughter Caylee in 2008.

Casey Anthony previously said a baby sitter kidnapped the girl, but her attorney suggested a different set of events during his opening statement.

Baez said Caylee and her grandmother swam most of Father's Day on June 15, 2008, and suggested that Cindy Anthony forgot to pull up a ladder that prevented the toddler from climbing into the pool on her own. Baez suggested that Caylee slipped into the pool the next day when no one was looking.

The distraught family panicked and didn't call police, he said.

"Casey should have called 911. That's what she's guilty of, she's not guilty of murder. This is not a murder case," Baez said.

A meter reader discovered Caylee's remains, some as small as a pebble, in a wooded area in December 2008 about a half-mile from where the child lived. Her skull was covered with duct tape that had residue from a heart-shaped sticker on it.

AP