ORLANDO, FL --Prosecutors focused Friday on what they believe killed 2-year-old Caylee Anthony in the Florida murder trial of her mother, as jurors heard testimony from the medical examiner who reviewed the child's skeletal remains and saw graphic video of how duct tape could have been used to suffocate her. Orange and Osceola County chief medical examiner Dr. Jan Garavaglia testified that she determined the toddler's manner of death to be homicide, though she encountered contentious cross-examination from Anthony's attorneys. The official cause of death she listed was "death by undetermined means," but Garavaglia said she applied a three-pronged test to arrive at her determination. She said she took into account not only the physical evidence present on the remains she examined, but all the information she had about how they were found and what she'd been told about the authorities' investigation. "We know by our observations that it's a red flag when a child has not been reported to authorities with injury, there's foul play," Garavaglia said. " ... There is no child that should have duct tape on its face when it dies." Casey Anthony is charged with first-degree murder. Prosecutors believe she suffocated her daughter in June 2008. She didn't report her missing for 31 days. The defense contends she drowned in her grandparents' pool. Her remains were found in a wooded area not far from the Anthony family home in December 2008. Garavaglia also bolstered chloroform evidence that was found by investigators inside the trunk of Casey Anthony's car. She testified that even a small amount of chloroform would be sufficient to cause the death of a child. Defense attorney Cheney Mason tried to poke holes in Garavaglia's findings, getting her to admit that toxicology tests on the bones came up negative for "volatile chemicals." Still, she stuck by her conclusions even when Mason tried to suggest the idea of an accident. "You're trying to tell this jury 100 percent that this death couldn't be an accident?" Mason asked at one point. "Accidental deaths are reported 100 percent of the time -- unless there's reason not to," Garavaglia responded. Later in the day, the defense objected to hearing testimony from University of Florida professor and human identification laboratory director Michael Warren, who planned to present a computer animation of the way duct tape could have been used in the death. The animation featured a picture of Caylee Anthony taken alongside her mother that was superimposed with an image of her decomposed skull, and another with a strip of duct tape that was recovered with her remains. The images were slowly brought together showing that the duct tape could have covered her nose and mouth. "This disgusting superimposition is nothing more than a fantasy," lead defense attorney Jose Baez said while arguing against it. "...They're throwing things against the wall and seeing if it sticks." Following a short recess to review some case law offered by the defense, Perry ruled that the video could be shown to the jury. When it was displayed, jurors were glued to their monitors and several could be seen taking notes. Warren testified that it was his opinion that the duct tape found with Caylee's skull was placed there before her body began decomposing. The day's testimony concluded with the prosecution calling a pair of crime scene investigators who collected insect evidence from a bag of trash found in Casey Anthony's trunk and bugs found at the scene of Caylee's remains. Baez ended the day by making a motion for a mistrial, based on Perry allowing the computer animation evidence. The motion was denied. Earlier in the day Casey Anthony broke down in tears and started shaking when a professor of anthropology testified that some of her daughter's bones had been chewed on by animals. She was immediately comforted by defense attorney Dorothy Simms. Professor John J. Schultz of the University of Central Florida, told jurors how a team of forensics people carefully searched the wooded area, marking with tiny flags the locations where the child's bones were found. Perry ended proceedings about 90 minutes early Thursday after Anthony felt sick and had to leave the courtroom. Jurors also saw photos of the tattered and torn shorts and shirt Caylee was wearing when she died. Later, as they viewed pictures of Caylee's bones, Anthony looked down, covering her mouth with her fist.