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McALLEN, Texas (CNN) -- An auto safety expert testified Saturday in a $1 billion lawsuit against Bridgestone/Firestone that a flaw in the design of the Ford Explorer -- and not the vehicle's Firestone tires -- caused the accident that injured four members of a south Texas family last year.

Defense witness Chris Shapley told the court a tire blowout should not have caused the vehicle to lose control and roll over.

With testimony ended for the weekend, the defense is expected to call more witnesses Monday and conclude its introduction of evidence. Closing arguments are likely to begin Tuesday and the jury could get the case the same day.

"We're coming along in this case, and soon, probably early this week, this case is going to be in your hands," Judge Filemon Vela told jurors Saturday.

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Before court concluded, the judge instructed jurors not to read or watch anything dealing with the case.

Bridgestone/Firestone is being sued by the family of Marisa Rodriguez, 41, who was left wheelchair-bound when her family's Explorer flipped over on a Mexican highway on March 9, 2000.

The family reached an out-of-court settlement with Ford in July for a reported $6 million.

Thomas Black, a Ph.D. and "human factors consultant" who once worked for General Motors, also supplied expert testimony for the defense on Saturday. And defense attorneys read aloud a deposition from Ford engineer Allan Rauner supporting their argument.

Bridgestone/Firestone CEO John Lampe testified Friday that claims data submitted to the company -- reports of tire defects resulting in injuries or lawsuits -- showed eight times as many claims for tires on Explorers than the same tires on Ford Ranger pickup trucks.

Marisa Rodriguez was paralyzed in the accident.

"I'm not looking to fight with Ford, but doggone it, we have to look at the vehicle," he said. "If you want to get to the problem, you have to look at the tire, and you have to look at the Explorer."

The accident occurred five months before Firestone announced the recall of 6.5 million 15-inch Wilderness AT, ATX and ATX II tires made at the company's plant in Decatur, Illinois, where the Rodriguez's tire was made.

The National Highway Traffic Safety Administration has documented 203 deaths and more than 700 injuries linked to tread separation rollover accidents involving Firestone tires and Ford Explorers.

Ford blames the problem on faulty tires. Firestone blames it on design flaws in the popular Explorer. The dispute led the companies to sever their century-old business relationship this spring.

-- CNN Producer Carol Yancho contributed to this report.