A lawyer for Toyota Motor Corp. staked out the company's most aggressive stance so far in its sudden-acceleration saga, citing driver error as a likely cause of many fatalities that have been tied to the issue.

The attorney, Joel Smith of law firm Bowman & Brooke LLP, said that most of the 48 deaths a safety expert has blamed on sudden acceleration involved drivers who were elderly, had medical issues, were distracted or navigating slippery roads.

"All of these are tragic situations," Mr. Smith said in a web conference with reporters. "What this actually does is indicate a very familiar pattern—a familiar pattern reflected in every study done on sudden acceleration in past years."

Toyota said faulty electronics—which plaintiffs say is a cause of sudden acceleration—had nothing to do with the cases of its vehicles accelerating out of control. But Toyota's blunt stance Thursday indicates the Japanese auto maker is digging in for a long fight as the sprawling litigation in federal court in Santa Ana, Calif., trudges forward.

Hundreds of drivers have sued Toyota saying their vehicles have lost value in the wake of millions of world-wide recalls prompted by complaints of sudden acceleration.

Toyota's recalls have involved sticky accelerator pedals and bulky floor mats. Several weeks ago the company settled one high-profile case, a crash last year that killed a California highway patrolman and his family when the accelerator became trapped in a floor mat.

For Toyota, blaming drivers is dicey from a public-relations perspective. A 1989 study of similar sudden-acceleration incidents at Audi AG, a unit of Volkswagen AG, blamed drivers. Audi was ultimately exonerated of building defective cars. But its sales and reputation took a huge hit.

The Wall Street Journal has reported that federal regulators have accumulated data suggesting many sudden-acceleration incidents in Toyotas were caused by drivers mistakenly stepping on the gas pedal.

Toyota's comments Thursday were tied to a report produced by auto-safety advocate Sean Kane, who is backed financially by several plaintiffs' attorneys. Mr. Kane's study used data reported to federal regulators to identify what he says are 48 deaths in Toyota vehicles attributable to sudden acceleration.

Toyota says one case involved a driver who lost control of the vehicle in heavy rain, killing a passenger who wasn't wearing a seatbelt. Another involved a woman who crashed as she was reaching in the back seat to assist a small child. In another crash the insurance company indicated the driver likely was blinded by the sun, Toyota said.

"If they have concluded this about these 48 cases, what they should be doing is proffering the evidence," Mr. Kane said. "All they're doing now is talking."