Intuitive Surgical Inc. prevailed in a civil lawsuit that accused it of negligence in its training of doctors using the company's surgical robot machines, a victory as it looks to counter criticisms that its da Vinci machines are unsafe and too costly.

The suit, filed in Kitsap County in Washington state, had sought $8.45 million in compensatory damages in connection to the death of Fred Taylor, who had his prostate gland removed with a da Vinci robot in 2008 and died four years later. The plaintiffs alleged that complications that occurred during the surgery were the cause of Mr. Taylor's death.

A jury, however, decided Intuitive hadn't been negligent in its training of the surgeons who performed Mr. Taylor's prostate removal, the culmination of a five-week trial that examined the company's training and marketing practices.

Intuitive's stock price has been under pressure in recent months as investors have grown more concerned about criticism of the da Vinci's cost-effectiveness and safety. The verdict Thursday seemed to ease some of that pressure, and Intuitive shares rose 3.7% to $496.02 in after-hours trading.

"We are pleased with the jury's verdict," the company in a statement. "Intuitive Surgical's technologies have extended the benefits of minimally invasive surgery to over 1.5 million patients around the world. We will continue our commitment to patients, surgeons and hospitals to uphold the highest standards of safety."

Intuitive's robots are operated by surgeons sitting at a computer, where they remotely control the robot's arms. The machines, which can cost more than $1 million each, are marketed as less invasive than traditional surgeries and have helped Intuitive reach $2.17 billion in sales last year. However, some studies have questioned the cost-benefit of the procedures compared to minimally-invasive surgeries performed by hand. The company also faces more than 20 other product-liability suits, according to regulatory filings.

The estate of Mr. Taylor alleged the man's surgeon hadn't been properly trained in performing prostate removals with the da Vinci machine. The September 2008 surgery was the first unassisted procedure performed by the lead surgeon using the da Vinci machine, and Mr. Taylor died four years later as a result of resulting complications, including a rectal injury, the plaintiffs alleged.

Intuitive's lawyers argued the company informed the doctor not to perform surgeries on patients who were obese until the doctor was more experienced, and that the surgeon decided on his own to ignore the warning. The company also claimed the rectal injury occurred after the da Vinci surgery was performed.

Intuitive's victory could ward off future jury trials from other plaintiffs and deter additional suits, said Spencer Nam, a Janney Capital Markets analyst. Some attorneys and plaintiffs may instead pursue smaller monetary settlements rather than risk the chance of losing in court, he said.

"This outcome could potentially turn some of those cases into a quick settlement of some kind," Mr. Nam said. "If they had lost, it's possible that new cases could have come out of the woodwork."

Earlier this month, the company sent customers a medical notice about a potential defect in a scissor instrument used with its robots. In February, a study found robotic surgeries were no better than minimally invasive hysterectomies performed by hand. Since then, the da Vinci's safety also has come under question in lawsuits and media reports noting a rise in adverse event reports to the U.S. Food and Drug Administration, which the regulator has been probing through physician surveys.