Sources: Duct Tape Used To Kill Caylee

ORLANDO, Fla. -- Sources close to the investigation said that a group of new pictures released Tuesday include images of what prosecutors said is the murder weapon used to kill Caylee Anthony.

According to sources, a strip of duct tape found on Caylee's mouth is one of three prosecutors believe were used by Casey Anthony to suffocate her daughter.

Anthony's defense maintains the tape is just a theory and the state has no definitive proof of the murder, citing that the state failed to find Anthony's prints on the duct tape.

"The biggest problem for the defense is that there can never be an innocent explanation for duct tape being fixed on a child's face," Orlando defense attorney Richard Hornsby said.

Hornsby said that the number of pieces of tape and where they were placed is critical.

"The fact that there was more than one piece and they were used to block the airways, clearly that's where the state is going to argue the premeditation comes from," Hornsby said.

The state attorney has denied comment, but in a December hearing, prosecutor Jeff Ashton first laid out his theory.

"Maybe her killer saw her eyes as she applied one piece, then two, then three so that no breath was possible," he said. (Watch The Hearing Video)

Hornsby also said that the defense is validating the state's theory by trying to cast doubt on Roy Kronk, the former meter reader who discovered Caylee's remains.

"The defense pointing at Roy Kronk as having used duct tape, they're admitting to tape being affixed to her face and Caylee suffocating," Hornsby said.

Also amid the documents released are photographs of the trunk liner taken from Anthony's white Pontiac and the rare Henkel brand of duct tape found on Caylee's small skull. The same type of tape was used by the Anthony family to put up fliers of Caylee when she was missing.

Enlarged photos showed a knife with a strand of something sticking to it. The photos were submitted to an FBI laboratory for testing, but the knife could not be linked to the duct tape.

The trunk liner photographs showed a flaky substance and what look like small stains. Larger stains are visible on the back of the liner.

Casey Anthony, 23, is in the Orange County Jail on no bond. She is charged with first-degree murder in the death of her daughter.

Caylee's remains were found in a wooded area off Suburban Drive near the Anthony family home in Dec. 2008.

Anthony maintains a nanny by the name of Zenaida Gonzalez kidnapped Caylee.

The judge in the case against Casey Anthony has turned down a request from the prosecution for a private hearing without the defense present.

Jose Baez told WESH 2 that Judge Stan Strickland has ruled that Anthony's defense should be allowed to be present at that closed door hearing.

In court papers, the prosecution said they had new evidence they felt they could only share behind closed doors without the defense or media present.

Strickland has yet to set a date on when that hearing will happen. It is unknown what that evidence is.