Tune in to HLN's "Nancy Grace" at 8 ET Tuesday night for new details on the trial of Casey Anthony. Follow the details as they happen at our special Casey Anthony trial page.

(CNN) -- Two-year-old Caylee Anthony was not murdered by her mother as prosecutors maintain, but drowned in the family's pool in June 2008, Casey Anthony's defense attorney told jurors during opening statements Tuesday.

Casey Anthony and her father, George Anthony, panicked upon finding the child, Jose Baez said. Anthony found her father cradling Caylee's body the morning of June 16, 2008, he said, and George Anthony yelled at his daughter, "Look what you've done. Your mother will never forgive you." He told her she would go to jail for child neglect, Baez said.

"This is a tragedy that snowballed out of control," Baez said. "This is not a murder case. This is not a manslaughter case ... this is a tragic accident that happened to some very disturbed people."

Anthony is accused of killing Caylee in 2008 and lying about it to investigators. The Orlando trial, which comes after nearly three years of legal twists, turns and delays, has garnered interest nationwide.

Anthony has pleaded not guilty, and denies harming her daughter or having anything to do with her disappearance. Baez has said that once all the facts are known, it will become clear his client is innocent.

In addition to capital murder, Anthony faces six other charges, including aggravated child abuse, aggravated manslaughter of a child and providing false information to authorities. If she is convicted by jurors -- seven women and five men along with five alternates -- she could face the death penalty.

Baez dropped another bombshell when explaining Anthony's behavior in the month before Caylee was reported missing on July 15 -- partying and lying about the child's whereabouts. "Casey did what she's been doing all her life, or most of it: hiding her pain," he said, adding that Casey Anthony had been sexually abused by her father starting at age 8.

Anthony was taught from an early age to behave as if nothing was wrong, he said, describing an incident where she went to school and behaved normally at age 13 after performing oral sex on her father. George Anthony sat stone-faced in the gallery as Baez made the allegations; Anthony put her head on the shoulder of another defense attorney and sobbed.

However, in his testimony, George Anthony -- the trial's first witness -- denied ever sexually abusing his daughter. He also said he was not at his home when Caylee died. "If I'd have known something happened to Caylee, we wouldn't be here today," he said as Casey Anthony shook her head.

George Anthony said as a former police officer, he was trained in CPR and that he would have done everything possible to save his granddaughter's life if he had found her in the pool as Baez alleged.

Baez also alleged Casey Anthony was inappropriately touched by her brother, Lee, although "it didn't go as far" as it had with her father. It was bad enough, however, he said, that the FBI conducted a paternity test to see if Lee Anthony had fathered Caylee.

He told jurors the Anthony family "keeps its secrets quiet ... You're going to hear all kinds of bizarre family behavior."

Baez said the family was "religious" about removing the above-ground pool ladder so that Caylee, who loved to swim, had no access to it. He suggested that Caylee's grandmother, Cindy Anthony, had forgotten to put it up the night before Caylee drowned, as she and Caylee were just exiting the pool when Anthony arrived home.

The day after Caylee's death, June 17, Cindy Anthony told coworkers she believed someone had been swimming in her pool, as the gate was left open and the ladder was left in place, Baez said.

Baez attacked much of the state's forensic evidence, saying such evidence has never before been admitted into courts -- and a death-penalty trial should not be the test case, as much of it is "questionable."

Police zeroed in on Anthony from the beginning, he said. "This investigation was extremely thorough when it comes to focusing in on Casey, probably the most comprehensive investigation that you will ever come across, and in the history of the state of Florida. It was directed at one person and one person only. The problem with this investigation is, it reached a level of desperation."

During his two-hour opening statement, Baez also cast doubt on Roy Kronk, the meter reader who found Caylee's skeletal remains in December 2008, alleging that he found the remains in an unknown location months earlier and moved them to where they would be found by authorities in an attempt to cash in on the high-profile case. "He thought he had himself a lottery ticket," Baez said.

"You will not be able to trust a thing having to do with Mr. Kronk, because he had control of Caylee's remains, obviously, for several months," Baez said. "Where he found her we do not know. We may never know, because the police never investigated him."

Kronk's attorney, David Evans, denied the allegations in a statement. "To the extent that the defense is stating that Mr. Kronk somehow had possession of and had something to do with the disposition of the remains of Caylee Anthony, those statements are absolutely false," Evans said.

George Anthony's cross-examination by Baez was punctuated by objections from prosecutors, most of them sustained by Orange County Chief Judge Belvin Perry Jr.

Baez did elicit the information that George Anthony did not ask his daughter who had fathered her child until around the time Caylee was born.

George Anthony also said he never asked to meet the fictitious nanny, "Zanny," who Casey Anthony had claimed was named Zenaida Gonzalez. In the early days of the investigation, Casey Anthony initially alleged the woman had kidnapped Caylee, but authorities were never able to find the woman. George Anthony said he had no contact information for "Zanny."

Baez did not ask about sexual abuse, but George Anthony admitted to him he had heard the drowning theory before. Baez also attempted to cast doubt on George Anthony's recall of what Caylee was wearing the day he last saw her, suggesting he would likely not have retained that detail as he didn't know it was the last time he would see her. George Anthony completed his testimony on Tuesday but could be recalled to the stand later.

After Tuesday's court session, an attorney for George and Cindy Anthony issued a statement responding to Baez's claims made during his opening remarks.

"George and Cindy Anthony are shocked and appalled that the Defense would resort to lies about them in today's opening statement. Baez's idle speculation today certainly are not facts, The only result achieved by the Defense in this statement was to further hurt this grieving family, " Orlando attorney Mark Lippman said in the written statement.

"George Anthony maintains that he never had anything to do with the death of Caylee Marie Anthony including what happened to her remains after she allegedly drowned," Lippman added.

In an appearance later Tuesday on HLN's "Nancy Grace," Lippman was more pointed in his remarks, saying Baez's accusations were "all just fiction. His opening (statement) was fiction and there's nowhere to go with it."

''Everything he (Baez) said about George was a complete and utter lie, and I am, for one, very proud of my client for being able to sit there as he did and just be able to take what was said about him without showing the reaction that I felt myself on his behalf,'' Lippman added.

Now 25, Casey Anthony wore a loose-fitting white shirt while she sat at the defense table for the first day of her trial. Her hair was pulled back in a ponytail, then put into a bun for the afternoon session.

Earlier, prosecutor Linda Drane Burdick told jurors that while it may be difficult to accept that a mother could kill her own child, there is no other conclusion that can be drawn, based on the evidence.

"No one but Casey Anthony had access to all the pieces of evidence in this case," Burdick said. "... No one else lied to their friends, to their family, to investigators. No one else benefited from the death of Caylee Marie Anthony. Caylee's death allowed Casey Anthony to live the good life -- at least for 31 days."

Anthony, who was 19 when her daughter was born, "appeared to all outward observers to be what her parents thought she was -- a loving mother working hard to provide support for her daughter," Burdick said. "But as the evidence in this case and the investigation into the background of Casey Anthony will show, that was an illusion." Anthony's parents thought she had returned to her job at Universal Studios after maternity leave, Burdick said, and indeed she dressed daily in work clothes and had a Universal Studios ID, but went "who knows where."

Caylee visited her great-grandfather on June 15, 2008 -- Father's Day -- and a photograph was taken of the two together, Burdick said.

"The next time a photograph was taken of Caylee Anthony is on December 11 of 2008, (when her remains were found)," Burdick said as Anthony frowned, shook her head and wiped tears off her cheeks.

"The story of this case is not about Casey Anthony. It is about what happened between the photograph taken on Father's Day, June 15, 2008, and the photograph taken on December 11 of 2008. What happened to Caylee Marie Anthony? You will hear, during the testimony in this case, that no one had any idea anything had befallen Caylee Marie Anthony until July 15 of 2008. How can that be? What happened between June 16 and July 15? Where was Caylee Marie?"

Burdick took jurors through that 31-day period before the little girl was reported missing, detailing Anthony's lies to her friends and her increasingly frantic parents, George and Cindy Anthony, regarding Caylee's whereabouts. She also talked about Anthony's getting a tattoo during that time -- "Bella Vita," Italian for "beautiful life" -- and referenced photographs of her partying at local clubs.

Baez told jurors, however, they were not in court "to talk about day 1, day 2, day 3, day 4. We're not here to talk about how foolish Casey acted. We're here to find out exactly how Caylee died. That's the key issue throughout this entire case."

Burdick told jurors they would hear in detail about evidence including a stain in Anthony's car trunk and the odor of human decomposition emanating from it, as well as her misleading statements to authorities during the investigation into Caylee's disappearance.

Prosecutors allege Anthony used chloroform -- evidence of which was found in her car trunk by technicians -- on the little girl before putting three pieces of duct tape over her mouth and nose, cutting off her air supply. They allege she then stashed the body in the trunk of her Pontiac Sunfire before disposing of it.

A cadaver dog alerted to the presence of human decomposition in the trunk, Burdick said, and a scientist will testify that air samples from the trunk were also similar in chemical composition to human decomposition. A search of a computer in the Anthony home showed that someone had searched for information on chloroform and how to make it, along with other searches.

Anthony explained the odor by saying there was a dead animal caught in the frame of the car, Burdick said. She eventually abandoned it, saying it had problems and had run out of gas. On June 30, it was towed to a wrecker yard, where it stayed until July 15, when Anthony's parents picked it up and drove it home.

Defense attorney Baez told jurors they would hear about "false positives" with cadaver dogs, and suggested it and the other evidence were "questionable." Anthony did some "ridiculous, stupid things," he said, but "there's not one piece of evidence, one single thread of evidence that links Casey to Caylee's body."

At 5 a.m., more than 30 potential spectators were lined up to get tickets to get inside the courtroom, according to In Session producer Nancy Leung. In an hour, that number had swelled to more than 50 -- with a full three hours to go before court began.

The jury was seated Friday after the process was moved to Clearwater, Florida, in Pinellas County out of concerns that an impartial jury could not be seated in Orlando, in Orange County, because of the intense media attention surrounding it.

HLN's "Nancy Grace" producers Philip Rosenbaum and Lee Alexander contributed to this report.