An FBI technician testified Thursday in the Casey Anthony murder trial that duct tape found on 2-year-old Caylee Anthony's body was contaminated during testing by another technician.

Anthony, a 25-year-old Florida mother, is on trial for first-degree murder in the 2008 death of her toddler daughter Caylee. She has pleaded not guilty. 

Heather Seubert, who worked in the forensic DNA analysis unit at the FBI when she examined evidence in the case, testified that DNA on duct tape at the crime scene did not match Caylee or her mother or grandparents. 

Seubert was the second witness to testify for the defense Thursday, which began to present its case claiming Anthony did not kill the child. The prosecution wrapped up its case Wednesday. 

Seubert also testified that she found no blood or DNA on stains taken from the clothes and car of Casey Anthony. 

"Brown and yellow areas were identified throughout as possible stains," Seubert said when speaking about testing done on stains from inside the trunk of Anthony's car. All stains tested were "negative for the presence of blood," Seubert told jurors. 

But prosecutors say Anthony suffocated the girl by placing duct tape over her nose and mouth -- a manner of death that would likely leave no trace of blood, forensic experts say.  

Defense attorneys, meanwhile, claim Caylee drowned accidentally in her grandparents' swimming pool and that Anthony's father disposed of the body.

Caylee's skeletal remains were found in December 2008 -- five months after she was reported missing -- in a wooded area near her Orlando home. No cause of death has been determined, but prosecutors point to duct tape found on the girl's skull in arguing their case against Anthony. 

Earlier Thursday, the defense called crime scene investigator Gerardo Bloise, who previously testified for the prosecution. Bloise had processed items seized from Anthony's bedroom. 

If convicted on first-degree murder charges, Anthony faces a death sentence.

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