Three weeks into the Casey Anthony trial, some mysteries appear tougher to unlock than ever before. Who killed toddler Caylee Anthony will be resolved at the trial, but not apparently who fathered her.

While the Caylee Anthony homicide trial is focused on establishing that Caylee's 25-year-old mother Casey Anthony murdered her in cold blood, there is no clarity on who fathered her. Even Casey herself can't be of much help as she just doesn’t know!

The court witnessed dramatic scenes on Thursday when the defense attorney made a shocking suggestion that Casey's brother Lee could have been Caylee's father. It then emerged that both Lee and Casey’s father George had undergone DNA tests to determine if they had fathered Caylee. Tests showed both were not.

The mystery goes back to 2005 when she was pregnant. Casey had told her friends that she did not know who was the father of the baby in her womb. ... it was just a random one night thing, she told a friend.

Around this time she started dating Jesse Grund, who believed that he was the father of the child. However, DNA tests done after Caylee's death proved that he was not the father. For the first year or two of her life, I was dad ... I was the father figure in her life, and I loved her more than anything. She was an amazing little baby. I had never been a father before, he recollected in a 2009 interview.

Focus then turned on to another person who Casey had dated in 2007, Jesus Ortiz. Ortiz had died in a car crash in 2007 and some of Case's friends believed he was the father of Caylee. But Ortiz' family vehemently denied this.

Miss Anthony never told the family Jesus was the father or that he might be the father ... In fact, the family has never met her and does not know her, the family said in a statement.

With Caylee's death truth could remain wrapped in mystery.

Casey Anthony is accused of murdering her daughter by applying chloroform first and sealing her mouth with duct tapes, looked away.
Casey Anthony denies the charges that she murdered her toddler daughter. She contends that Caylee drowned accidentally in the swimming pool. If she is found guilty of first degree murder, Casey Anthony could be sentenced to death by lethal injection.

He story is that she lied about Caylee's death because she was 'conditioned to lie'. She had also accused her father of sexually abusing her for years when she was a child, a charge George has denied in court.

The prosecution says Casey killed the little girl by suffocation and kept the dead body in the boot of her for several days. She then dumped the body in the woods near her parents' home.

Earlier in the week, her mother Cindy Anthony took the witness stand testified against her daughter for the third time during the trial and helped prosecution identity things that belonged to the Anthony household.