Casey Anthony's defense team came out swinging this afternoon, when lawyers asked a DNA expert if law enforcement had ordered a paternity test to determine if Anthony's older brother was the father of her child.

Anthony, 25, is accused of multiple charges , including capital murder, aggravated child abuse, aggravated manslaughter of a child and misleading law enforcement in the case of the death of her daughter, Caylee. The prosecution is seeking the death penalty.

"Were you asked to conduct a paternity test for Lee Anthony as to being the potential father of Caylee Anthony," Anthony's attorney, Jose Baez, asked serology expert Heather Seubert.

Seubert, who worked in the forensic DNA analysis unit at the FBI in 2008, said she was assigned to the Anthony case and examined several key pieces of evidence.

Prosecutor Jeff Ashton immediately objected to Baez's question and Judge Belvin Perry quickly sent jurors to lunch and called a sidebar with the attorneys.

Ashton argued the line of questioning was irrelevant and not in good faith. He said it implied that law enforcement had requested the test.

Baez and Ashton got into a heated exchange about the subject, at which time Perry told the two men to lower their voices.

"I don't have a hearing problem and the amplification of questions, objections, I don't need them," Perry said.

Outside the presence of the jury, Seubert told Perry that Nick Savage, another FBI agent who was working on the case, asked her to conduct DNA tests in October 2008, to see if Anthony's brother, Lee Anthony, was Caylee's father.

Perry ultimately instructed Baez to revise his question and warned him not to ask questions that would lead to an inference. Perry added, "I'm not even going to venture a guess ... as to your motivation."

When the jury returned from lunch, the line of questioning continued.

"I wanted to ask you if you conducted, what would be considered a paternity test, to determine if Lee Anthony was the biological father of Caylee Anthony," Baez asked.

Seubert affirmed a DNA comparison had been made and replied, "Based on the STR typing results, the DNA obtained from ... Caylee Anthony could not have originated from a biological offspring of ... Lee Anthony."

Baez did not ask Seubert if the same test was conducted on Casey Anthony's father, George Anthony. As a result, jurors are unaware her father was also tested and excluded.

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The powerful testimony about paternity is largely considered a win for the defense who, up until today, were unable to get testimony before the jury about alleged abuses they claim Casey Anthony suffered.

During opening arguments , Baez claimed Caylee died on June 16, 2008, when she drowned in her family's swimming pool. He said Anthony did not contact the authorities because she was unable to tell the truth after years of sordid sexual abuse that she suffered at the hands of her own father.

"It all began when Casey was eight years old and her father came into her room and began to touch her inappropriately and it escalated ... She could be 14 years old, have [had] her father's penis in her mouth, and go to school and play with the other kids as if nothing [had] happened," Baez said.

The defense attorney also took aim at Lee Anthony, alleging he tried to "follow in his father's footsteps."

"On certain occasions when he was a teenager, [Lee] attempted to also touch his sister, although it didn't go as far," Baez said, adding, "These ugly secrets will come out at this trial. And you'll see what makes Casey Anthony act the way she does."

Baez tried to make good on his promise during the third day of the trial when he attempted to question Anthony's ex-boyfriend, Anthony "Tony" Lazzaro, about a conversation he allegedly had with Anthony in June or July of 2008. Lazzaro said she told him that Lee Anthony had attempted to "feel her up."

Lazzaro said he could not recall if Anthony had offered a time frame for when the alleged abuse had occurred, but said it was "definitely in the past ... not anything in the present."

Lazzaro also said that Anthony told him that her father, George Anthony, had physically abused her.

"Hitting -- that's all I can remember," Lazzaro said.

Perry ultimately ruled the jury would not be able to hear the testimony.

Today's testimony, however, may leave questions in the minds of jury as to why someone in law enforcement would have even been curious whether Anthony's brother could have potentially been the father of her child.

Earlier Thursday, Seubert reported she tested swabs taken from items in the trunk of Anthony's car, including the spare tire cover and the trunk liner. All of those items were tested for the presence of blood and were negative, the expert testified.

In addition to testifying about Anthony's vehicle, Seubert said she also examined several items that were taken from Anthony's closet, including clothing investigators believe she wore on June 16, the day Caylee was last seen alive. While several of the items had faint stains, all were negative for the presence of blood, she said.

Since the beginning of the trial, prosecutors have dismissed the defense's explanation of Caylee's death and have claimed Anthony killed her child by placing duct tape over her mouth. Duct tape was found wrapped around Caylee's skull when a county worker found her remains on December 11, 2008.

Toward the end of her testimony today, Seubert testified that the duct tape -- a vital piece of evidence in the case -- had been contaminated. During testing, DNA found on the tape did not match any members of the Anthony family. Instead, it was found to be a match with another forensic examiner who had analyzed the duct tape.

Today's testimony marked the third anniversary of Caylee's reported disappearance.

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