Casey Anthony's trial entered its 20th day with Jose Baez, Casey's lawyer trying to shred the prosecutor's evidence into pieces by suggesting that the allegation that Casey had used a duct tape as a murder weapon to suffocate her 2-year old daughter Caylee is false even as the toddler's father's identity came into focus.

On Thursday, Lorie Gottesman, an FBI forensic document examiner, testified that she did not see any match between the black plastic bags that contained Caylee's remains and similar black bags seized from the Anthony home.

Gottesman said the only traceable DNA evidence found on the duct tape belonged to her and she had no clue how it happened or when.

The forensic specialist also said she had examined the duct tape that was allegedly used by Casey to suffocate Caylee.

Earlier this week an FBI fingerprint expert Elizabeth Fontaine had testified that she had noticed the outline of a heart on the duct tape but later when she attempted to photograph the outline, it had disappeared.

Gottesman said on Thursday she used a high-tech device with special lights and filters that is capable of identifying images that are beyond the range of the human eye to see. However, she said she was unable to detect any sticker or sticker fragment, sticker residue on the duct tape.

Gottesman's testimony is important as the prosecutors suggest Caylee's killer had stuck a heart-shaped sticker on the murder weapon i.e. the duct tape and it could be useful in identifying the killer.

The heart-shaped outline is not the only thing the prosecutors are trying to tie Caylee's killer with. They said investigators had also found a heart-shaped sticker stuck on a piece of soiled cardboard found near Caylee's remains in the wooded area near the Anthony home.

However, Baez is trying to convince the jury that the duct tape and the cardboard are not associated with Caylee's remains or the crime scene.

On Thursday, Ron Murdock, crime scene investigator of the Orange County Sheriff’s Office testified that the cardboard was discovered about 30 feet away from the toddler's remains. Another witness, crime scene technician Jennifer Welch said the wooded area where Caylee's remains were found was littered with trash of all sorts.

An FBI DNA expert, Heather Seubert, also testified on Thursday that she was asked by the investigators to confirm whether Casey's brother Lee Anthony could have been Caylee's father.

Seubert said she had compared the DNA profiles and came to the conclusion that Lee was not Caylee's father. However, her testimony was important as Baez claims Casey was a victim of sexual abuse. He claims Casey was sexually attacked by her father George as well as her brother Lee on different occasions and it has influenced her self-denial and emotionless behavior.

Seubert also testified that she found little trace or no blood in the numerous pieces of evidence that she had tested, including the clothing and the laundry bag found with Caylee's remains and in th trunk of Casey's car. On cross examination, she said because there was no presence of blood does not mean that a crime did not occur. She said it is possible that blood could have leaked out in early stage of decomposition of human body and so if a body was in a bag in the trunk of a car and there was a hole in the bag, the blood could have ended up on the carpet.

The DNA expert also said that if a duct tape had been used to suffocate Caylee, her DNA should have been found on the sticky side of the tape. However, she acknowledged that the humidity and wet conditions in the swampy area where Caylee's remains were found could have degraded any DNA over the course of six months.

Earlier on Thursday, Orange County crime scene investigator Gerardo Bloise showed the jury photos of Casey's bedroom and her clothes that were found in a closet. He said he had examined a pair of trouser belonging to Casey, which she wore on June 16, the day Caylee was last seen alive. Bloise said he examined the photos using an alternative light source to detect stains but could find none. Upon cross examination, he acknowledged that Cindy, Casey's mother, had washed the trouser between June 16, 2008 and the day he had examined it

Thursday's final witness was FBI section chief of scientific analysis Cary Oien who testified that a small fragment of hair found on the shaft of a shovel Casey had borrowed from a neighbor was sent for mitochondrial DNA analysis but he is not aware of the results. Discovery documents filed by the prosecutors suggest that the hair did not belong to Casey or Caylee.

About Casey Anthony Trial

2-year old Caylee was last seen alive on June 16 and it was only on July 15 that she was reported missing by her mother Casey Anthony to the police. Cindy, Casey's mother had also alerted the police by calling a 911 dispatcher and saying that she had smelled a dead body in the trunk of Casey's car that was spotted in an impound lot. The car was later towed by authorities for forensic analysis.

Initially, Casey told the police that a babysitter called Zenaida Fernandez-Gonzalez (Zanny the nanny) had abducted Caylee. Investigations showed Casey was lying as the babysitter Zanny was fictitious. Five months later, in December 2008, Caylee's decomposed skeletal remains were found in a wooded area near the Anthony home by a meter reader who was relieving himself.

The prosecutors say Casey chloroformed Caylee and then put duct tape over her nose and mouth, suffocating the girl.

Casey's lawyers claim Caylee was not murdered. They say the toddler accidentally drowned in the family swimming pool and George, Casey's father, helped her keep the death a secret. George has denied the claim.

Casey has been charged with seven counts, including first degree murder, aggravated child abuse and misleading the police in the death of Caylee. If she is convicted of first degree, she could be sentenced to death by the seven-woman, five-man jury. The trial is expected to take another 2-3 weeks before a verdict is reached.