(Courtesy photo: AMC Studios)

The upcoming trial over a death on the set of the "Walking Dead" zombie drama will hinge on one key question: What happened in the moments before a stuntman plunged off a balcony and missed an airbag 20 feet below.

Lawyers for the AMC television series and its producers have argued that they are not to blame and that John Bernecker assumed the risk of his dangerous job. But lawyers for his parents, Susan and Hagen Bernecker, say something went wrong on that balcony.

The family's wrongful death lawsuit alleged that an actor who was supposed to fake shooting, then grabbing and pushing the stuntman off the balcony, instead made actual physical contact—which changed the trajectory of the fall. They are suing AMC Networks and Stalwart Films.

"Negligence on the stunt is the heart of the case," said Jeffrey Harris of Harris Lowry Manton in Savannah and Atlanta, who represents the Berneckers. "At the end of the day, it's going to be a straightforward question of whether the actor and the production company were negligent in the way they set up the stunt."

Harris represented the family of camera assistant Sarah Jones over her 2014 death while filming "Midnight Rider" near Savannah. After years of litigation, the family reached a confidential settlement with CSX Transportation in January. The undisclosed payment satisfied a $3.9 million judgment against the railroad resulting from apportionment of a 2017 verdict totaling $11.2 million. It concluded the case against the last of a series of defendants involved in the train crash on the set of a movie about musician Gregg Allman.

The "Walking Dead" trial is set to open Dec. 9 before Judge Emily Brantley in Gwinnett County State Court.

AMC and Stalwart are represented by Jackson Dial, David Dial and Joshua Wood of Weinberg Wheeler Hudgins Gunn & Dial. They deferred to a company spokesman, who shared an emailed statement.

"This was a tragic accident, and we have and continue to express our deepest condolences to the family of John Bernecker," the company said. "As it relates to the litigation, we will let our legal and factual defenses speak for themselves."

The judge has already denied a series of pretrial defense motions to throw out the lawsuit and a key expert witness whose testimony will support the plaintiff's theory of the case.

"Defendants argue that Bernecker was an experienced stunt man and that he knew what he was doing and had been hurt on stunts many times before," the judge said in her order denying the company's motion to dismiss. "In other words, Bernecker knew the risk of his profession and voluntarily engaged in this act—even assuming the risk that another actor's negligence in touching him and possibly affecting the trajectory of his fall could occur. The court does not agree."

The expert the defense attorneys attempted to exclude is Conrad Palmisano, an experienced stunt performer and coordinator. Palmisano has testified by deposition that video of the fall shows that an actor who was supposed to fake grabbing and pushing Bernecker actually touched him, according to the judge's orders. Palmisano's testimony is expected to include his opinion that the contact fatally changed the equation of the fall.

"The court finds this testimony acceptable for consideration by the jury, as he is an expert in the field," the judge said in an order dismissing the challenge, "His opinions are subject to cross-examination and the jury can accept or reject them out of hand."

The case is Bernecker v. Stalwart, No. 18-C-00435-1.