ORLANDO, Fla. -- A veteran investigator in the case of missing Caylee Anthony describes the child's mother as one of the toughest individuals he's ever run into, according to Orange County Sheriff Kevin Beary.

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Casey Anthony, who is the only person named as a suspect in her daughter's disappearance, has provided what investigators have called "deceptive responses" in connection with the case.

In an exclusive interview with Local 6, Beary said lead detective Sgt. John Allen has described Casey Anthony's attitude.

"I've had some very experienced people working on this case and Sgt. John Allen is one of those," Orange County Sheriff Kevin Beary said. "Sgt. Allen said that's one of the toughest individuals he's ever come in contact with when it comes to attitude and as you called the poker face."

"In your heart, do you believe (Caylee) is gone -- she is dead?" Local 6's Mike Holfeld said.

"Well, my dad-instinct says you never want to give up," Beary said. "But the way the evidence is looking, that's probably what's going to be down the road."

"She's gone?" Holfeld said.

"She's gone," Beary said. "Every day that passes, everything in your gut instinct tells you we're not going to find that child -- at least not alive."

Evidence from the trunk of Anthony's 1998 Pontiac included traces of chloroform and DNA pointing to a body in the vehicle. Also, hair in the trunk was linked to the missing 3-year-old, Local 6 reported.

"You know, we know that something's wrong," Beary said. "We know something happened and that's why we are still building the evidential case for the future."

Bear said the evidence could play a criminal court showdown with Casey Anthony, Holfeld reported.

"Well, Florida has laws on the books like that," Beary said. "I think before anybody does anything, the state attorney, the sheriff's office, the Florida Department of Law Enforcement and the FBI will make sure that if that is the scenario, we will have all our ducks in a row for a good solid case."

Beary said that additional evidence is coming but he has asked investigators not to brief him until they are ready to release it.

The sheriff also said that he is hopeful that the case will come to a close before he leaves office in less than three months.

A national search continues for missing Caylee Anthony.

Watch Local 6 News for more on this story.