Casey Anthony's mother has a panic attack during questioning for new polygraph show and says she's confident her daughter knows what happened to three-year-old Caylee

Casey Anthony's mother suffered a panic attack when she was questioned about what really happened to her granddaughter during filming for a new lie detector test-based show.

Cindy Anthony struggles to breathe as she says she “100 percent believes” her daughter knows what really happened to three-year-old Caylee.

The young woman's remains were found in a garbage bag half a mile from the family's Orlando home, six months after she was reported missing in June 2008.

Her mother Casey was accused of murder but was eventually acquitted after a sensational trial in which she was dubbed 'the most hated woman in America' after photos emerged of her holidaying after her daughter went missing.

Now Cindy has agreed to take a lie detector test as part of a new A&E show looking at the unsolved case, which also features her husband George following claims by his daughter that he helped hide Caylee's body .

In a sneak peek, the grandmother becomes emotional while talking about her deceased granddaughter.

When asked if Casey knows what happened to Caylee, Cindy responds, “Yes, I believe that one hundred percent. I kept hoping she would confess and that's the only reason I put myself through all the drama.”

The devastated parent then begins to wipe away tears before continuing, “Since June 16, 2008, Caylee has been my number one priority as to what happened to her and getting her back.

“I lost Casey and my granddaughter that day, but Caylee was always the priority. That's been my whole focus this whole time and the goal is to get to the truth and sit here and listen to her keep making up different stories as she sees fit.”

She then stops and becomes overwhelmed with emotion, shuddering as she tells the interviewer that she finds it difficult to talk.

She continues to spiral before suddenly clutching her chest and announcing that she is having a panic attack.

Her breathing becomes irregular and she runs off to take her anxiety medication.

But the attack is too advanced and her husband has to come in and try to comfort her.

Cindy continues to gasp for air and warns George that she is about to pass out. He suggests they go to the hospital while encouraging her to breathe.

At the end of the clip, Cindy is forced to lie on the floor with her eyes closed in a desperate attempt to steady herself.

It comes after George broke down when asked about hiding Caylee's body during a lie detector test for the same show, 'Casey Anthony's Parents: The Lie Detector Test.'

The latest documentary comes a year after he was accused by his own daughter of dumping Caylee's body in the Florida woods near his home. She claimed he sexually abused her as a child and did the same to her daughter – allegations he strongly denied.

Casey was 21 years old at the time of Caylee's death, and she partied just days after her daughter went missing, although she later claimed she was working with her club promoter boyfriend at the time.

Caylee was last seen alive on June 16, 2008, and was reported missing to the Orange County Sheriff's Office by Casey's mother, Cindy, almost a month later on July 15.

During a 911 call, the grandmother told dispatch that she had not seen Caylee in 31 days and that she had smelled a foul odor coming from her daughter's car, as if a dead body had been inside.

Cindy also revealed that Casey had given inconsistent explanations when asked about the child's whereabouts. She later told her mother that she had not seen her in weeks.

Anthony was subsequently arrested and interrogated at the Orange County Jail on July 16, 2008.

During interrogation, Anthony lied to detectives and told them that Caylee had been kidnapped by a babysitter on June 9, that she had tried to find her and that she was too exhausted to tell the police.

She told investigators the babysitter's name was Zenaida Fernandez-Gonzalez. However, it was soon determined that Anthony had no babysitter and that the woman, an acquaintance of Anthony, had never met her daughter, or other family and friends.

Anthony was charged the next day with making false statements to law enforcement, child neglect and obstructing a criminal investigation. Initially, she was denied bail by the judge.

Her bail was initially set at $500,000 during a bail hearing on July 22, 2008, and she was released a month later when bail was posted by the cousin of a California bail bondsman.

Months later, in October, she was indicted by a grand jury on charges of first-degree murder, aggravated child abuse, aggravated manslaughter of a child and four counts of providing false information to police, and was arrested again.

Meanwhile, officers and thousands of volunteers have been scouring Orange County and Greater Orlando in search of the child, whose remains were eventually found in a garbage bag on December 11, 2008, while more remains were found in nearby woods near Anthony's home.

The remains were identified as belonging to Caylee about a week later.

During the trial, jurors acquitted Anthony of first-degree murder, as well as manslaughter and child abuse.

However, jurors found Anthony guilty of four charges of providing false information to police – charges that saw the mother receive a four-year prison sentence.

Anthony was given credit for time spent in prison and was released on July 17, 2011, 12 days after the end of the trial.

Since the trial, she has tried to keep a low profile and live a quiet life in South Florida, where she has tried to avoid the spotlight and the general public.

She now lives in West Palm Beach, where she currently works as a private investigator, and has maintained a social life by drinking with friends at local bars.

The new documentary special airs Thursdays at 9 PM ET on A&E and Lifetime.