SAN FRANCISCO — An armada of 24 patent infringement cases, filed against 37 defendants by a prolific plaintiff with a single patent, could all get tried separately.

Northern District Judge William Alsup refused to relate the 24 cases brought by Gregory Bender against companies from AT&T Inc. to Pioneer Electronics Inc. to IBM Corp. for infringing on his nearly expired patent on a type of electrical circuit. It means that each case will proceed in separate courtrooms with separate judges.

"Although the same patent is asserted in all 24 cases, these cases are not related," Alsup wrote in a Monday ruling. "These cases involve different defendant companies with different products."

Sometimes judges relate cases like these for efficiency's sake, and the patent lawyers working on the cases, which account for nearly the entire Bay Area patent bar, were surprised. But Alsup said his ruling actually reflected the "entrenched view of 'related' as applied in practice by the judges now sitting on our district court."

Alsup did offer defendants a chance to voluntarily coordinate phases of the patent cases, like claim construction and invalidity proceedings, a tactic not often used by judges. The group of volunteers would share the same defense — and could serve as a sort of test case for the rest of the defendants.

The turn of events could present some difficulties for Bender and his lawyer, Piedmont solo David Kuhn, who had tried to relate the cases after filing them separately in March . Patent lawyers say it could be difficult for a single lawyer to handle that many separate proceedings, especially if they go to trial.

But on Wednesday Kuhn confidently said, "I think we'll be able to handle it."

Bijal Vakil, a White & Case lawyer who's involved in the case, said it will benefit the defendants.

"This order demonstrates that patent plaintiffs will need to exercise thorough diligence prior to filing cases with multiple defendants and need to be prepared for the possibility that they may proceed as separate cases to trial," said Vakil. "These types of orders will allow defendants the opportunity to adequately defend their respective interests without being lumped together as a single party."

Still, most of the defendants supported relating the cases in front of Alsup, who has appeared somewhat skeptical of the patent suit. Separate trials would probably be more expensive for defendants, who wouldn't be able to coordinate their defenses.

Gregory Lippetz, a Jones Day lawyer who represents a clutch of the defendants, including IBM and Motorola Inc., said, "I believe Judge Alsup is an excellent judge who will force the plaintiffs to abide by our local rules, which in a case like this is to the defendants' advantage."

The plaintiff lawyer, Kuhn, has revealed little about the client who unleashed the torrent of lawsuits on the Northern District of California. But in his motion to relate the cases, Kuhn explained that the claims from Bender's patent on "analog amplifier technology architectures" could be infringed by products such as cell phones, computer equipment, network drivers, high-definition television sets, ultrasound machines, MRI machines, lab equipment, arbitrary waveform generators, audio amplifiers, video amplifiers, hard disk drives and many more.