Kate Woodruff walked away from the car crash essentially unhurt. But her 6-year-old brother Ethan was thrown from his booster seat, his mother alleges in a lawsuit, suffering a brain injury that has left him permanently disabled.

Kate, then 4, was riding in a child seat with a five-point harness. Ethan, however, was strapped in his booster seat using a small seat-belt extender.

The devices are designed to extend seat belts so they can be comfortably worn by overweight passengers. But the extenders are marketed online and elsewhere to parents for use as a safe way to buckle their children into booster seats. Ethan’s father, Ben, who was killed in the crash, decided to use one without realizing that the owner’s manual for his Nissan Juke explicitly warned against such use.

Beth Woodruff, the children’s mother, remembers waiting for her family to come home on that Friday evening in 2013. Then a neighbor called to say something was wrong at the end of their Knoxville, Tenn., street.

Woodruff saw the car, so badly damaged it was barely recognizable, and then she saw Ethan.

“He was on the ground, he was not moving,” Woodruff said. “He just looked broken and not right. He looked like a doll thrown on the ground.”

Woodruff is suing Ford, whose supplier made the extender, alleging the company knew the devices were being taken by a dealership employee and sold online, marketed to parents as suitable to use with child seats.

Ethan was injured six years ago, but similar extenders are still widely pitched to parents on Amazon and in eBay listings, part of what child-safety experts say is a growing category of knockoff car-safety products and others spuriously marketed as improving safety.

(Amazon founder and chief executive Jeff Bezos owns The Washington Post.)

Parents use the extenders to either allow their children to buckle themselves in or deal with booster seats that don’t easily fit in the back of their cars.

It’s not clear how widespread the practice is or if other children have been hurt, but parents discuss extenders in online forums and experts say they hear from parents seeking advice.

“My kids always struggle to put [on] seat belt while seating on booster seat. I bought one, but belt didn’t fit. Any recommendations on small extenders?” a user wrote on the official Tesla owners’ forum last year.

Another user directed the person to the website of the same company that sold Ben Woodruff his extender. “They work pretty well,” the second user wrote.

But despite interest from parents, the country’s federal highway safety agency, experts and automakers say the extenders should never be used with booster seats.

Woodruff alleges in her lawsuit that the extender failed completely, coming unbuckled when a vehicle hit her husband’s car and exerted pressure on the extender in a particular way. A video prepared by an expert witness for Woodruff shows how an extender can be unbuckled without pressing the button by bending it in a person’s hands.

Other experts say extenders can also change the fit of a seat belt in a way that can lead to other injuries.

“The geometry of the seat belt is very specifically designed,” said Alisa Baer, a pediatrician and founder of the Car Seat Lady, a safety advocacy organization. Baer said she regularly receives inquiries from parents about extenders and recently posted a notice on the organization’s website warning of the dangers.

“The only time a seat-belt extender should ever be considered is for a person whose body is large enough that they cannot buckle the seat belt,” Baer said. “It should never be used on children.”

For parents who are struggling, Baer said they should try to find a narrower booster seat. Floppy buckles can be held straight using a pool noodle, she said.

Beth Woodruff said Ethan had had trouble buckling himself in his dad’s car. The seat belt buckle was recessed into the seat where he couldn’t reach it from his booster.

“If [Ben Woodruff] had known, if it had been evident that using a seat-belt extender was not safe, he would never have used a seat-belt extender,” Woodruff said.

In her lawsuit, Woodruff alleges that the website where her husband bought the extender was being supplied by an employee at a Ford dealership who was able to order them in bulk at a few cents apiece.

Company documents Ford turned over to Woodruff’s lawyers, and reviewed by The Washington Post, show the automaker realized it had an issue with the extenders being diverted as early as 2008. Ford’s brand protection office developed a plan to tackle the problem, but Woodruff’s lawyers allege that it wasn’t properly acted on.

After Ford received an anonymous complaint in 2012, a company employee found an old message about the 2008 plan, writing, “I guess it walked out the door when Jeff did.”

In 2012, Ford began taking a fresh round of action, and emails from as recently as 2018 show employees continuing to monitor online sales and trading information with federal authorities.

But Woodruff’s lawyers allege in the lawsuit that the company didn’t do enough, rejecting an idea to buy back some 1.6 million wayward extenders that the lawyers calculated might have cost $32 million.

“Ford knew that parents were misusing its seat belt extenders in this fashion, yet Ford still did not warn against substantial risks to children that it knew existed, and Ethan Woodruff was seriously injured because Ford failed to adequately warn,” the lawyers wrote.

The company has argued in court filings that the chain from Ford to Woodruff is too tenuous — passing through a “rogue employee” and a third-party website before being used in another make of car — that it can’t be held legally responsible for Ethan’s injuries. The company’s lawyers said Ben Woodruff should have heeded the warnings available to him and questioned the evidence indicating that the extender failed.

A judge in Knoxville has allowed the case against Ford to go to a jury and a trial is scheduled for next year.

The lawsuit lists other defendants, including the driver of the vehicle that hit the Woodruffs and the company that sold the extender, which has settled, said Dan Stanley, a lawyer for Beth Woodruff. The judge ruled in favor of the manufacturer of the booster seat, a decision Stanley is contesting.

Despite the steps Ford began to take in 2012, extenders are still widely available online.

Baer attributed the rising interest in the devices to information spreading by word of mouth and on social media and their ready availability.

“These things are proliferating through channels that didn’t used to exist,” she said.

The owner of the website Ben Woodruff used couldn’t be reached for comment, but in forum postings, parents considering buying an extender have shared chat logs with company employees warning that they’re not safe to use with child seats.

Amazon and eBay did not respond to requests for comment.

“It’s worth noting that the seat-belt extender was not purchased by the Woodruffs from Ford or a Ford dealer and it was not used in a Ford vehicle,” a Ford spokeswoman said. “Seat-belt extenders are provided as a customer service to owners of Ford vehicles, and are designed to extend the length of a seat belt to allow larger passengers to buckle their belts, for use only in the front seats of specific Ford models.”

The dealership employee who was obtaining the extenders no longer works for Ford. His lawyer did not respond to a request for comment.

The manual for Ben Woodruff’s Nissan Juke said using a seat-belt extender with a child seat “could cause serious injury or death.” But the warning on the extender was vaguely worded — “Do not use extender unless it is physically required” — and the booster seat manual said, “contact your vehicle dealer for a seat belt extender.”

Beth Woodruff said she wishes the messages parents received were clearer.

“I hate the idea there’s anybody out there in a car driving around with a kid in booster using a seat-belt extender,” she said.

The National Highway Traffic Safety Administration said in a statement that it has jurisdiction over all motor vehicle equipment, including seat-belt extenders.

“All motor vehicle equipment — even where NHTSA has not adopted a specific regulatory standard — must be free of safety-related defects, and whenever NHTSA determines that any motor vehicle equipment presents an unreasonable risk to safety, the agency will not hesitate to take action to ensure that the equipment is recalled,” the statement said.

“In addition, NHTSA and the child passenger safety community recommend generally that aftermarket products should not be used with child restraint systems because adding extra materials may impair the performance of a child restraint in a crash,” the agency said.

Six years after the crash, Ethan is in middle school. His injuries required his mom, grieving her husband, to move hundreds of miles to Atlanta where he went through weeks of intensive rehabilitation.

“There was just so much. It was just doing the next thing in front of me,” Beth Woodruff said. “That was all I could focus on and do. Thinking long-term got really overwhelming and very scary. It was just about going to the next therapy.”

The trauma his brain suffered in the crash severely affected Ethan’s development, and Woodruff said he struggles with reading comprehension and understanding risk to the point that he gets hurt. He’ll never be able to drive a car, she said.

Nonetheless, Beth described her son as an upbeat kid who had a degree of independence and attends a regular school.

“I pretty much think Ethan is amazing,” she said.