Sexual assault. An accidental drowning. A coverup. That is the explosive defense strategy declared before the jury in opening statements in the sensational Casey Anthony first-degree murder trial.

Anthony, now 25, is accused of killing her daughter Caylee in June 2008, and not reporting her child allegedly missing for 31 days, eventually telling Orlando, Fla., investigators that Caylee had been kidnapped by her baby sitter.

Lead defense attorney Jose Baez shocked the courtroom by saying Caylee never had been missing; rather, he said, she had died accidentally in her grandparents swimming pool. And that Casey’s father George, Caylee’s grandfather, helped cover it up.

“As Casey came around the corner and went to the back she saw George Anthony holding Caylee in his arms. She immediately grabbed Caylee and began to cry and cry and cry and shortly thereafter George began to yell at her "look what you've done!" said Baez.

“She (Casey) cried and cried and asked for her father's help and shortly thereafter George did help."

Prosecutors then called George Anthony onto the witness stand, the state’s first witness in this death penalty trial. Immediately, prosecutors had to address for the jury the equally stunning revelation -- according to the defense -- that Casey Anthony was a victim of sexual abuse by her father beginning when she was 8 years old. And, in another bombshell, that Casey’s brother Lee also sexually fondled his sister.

"Did you ever sexually molest your daughter Casey?” asked prosecutor Jeff Ashton.

“No sir,” replied George Anthony.

“Were you present when Caylee Anthony died?”

“No, and when I heard that today it hurt really bad,” said George Anthony, on the verge of crying.

Prosecutors are aiming to convince this jury that Casey Anthony researched “chloroform” and “neck breaking” months before 2-year-old Caylee disappeared and eventually used chloroform to make Caylee go unconscious, then duct-taped her nose and mouth shut to suffocate her.

Prosecutors say Casey was a single mother who did not want to be a mother anymore, but instead wanted to party, be free and be single. So, Caylee had to be eliminated.

But in his 90-minute opening statement, Jose Baez, hoping to raise “reasonable doubt” about the state’s evidence, unleashed bombshell after bombshell, including this stunner: that Roy Kronk, the meter reader who discovered Caylee’s remains in the woods a short walk from Caylee’s grandparents’ house, actually discovered the remains in August of that year, removed them, hid them somewhere for a couple of months, planted them in the woods and then reported the “find” so that Kronk could cash in on a $250,000 reward.

And all of this was just in Day One of the guilt phase of this trial.

Legal observers say introducing the sex abuse and coverup claims against George Anthony is a risky strategy. Now that the jury has heard this, perhaps the defense will have to put Casey Anthony on the stand to hammer home this scenario. That gamble would allow prosecutors to cross examine the murder suspect. And much of the prosecution’s case is that Casey Anthony is a chronic liar, which the state has reams of evidence to back up.

This trial is expected to take 6 to 8 weeks, in what is perhaps the most investigated and salacious murder case in Florida history.