Even Paul Wagner’s attorney calls him a geek. Wagner runs his computer business from an office in his parents’ Silver Spring home. He lives with a bunch of roommates in Dupont Circle and loves a good convention that displays fast machines.

But he’s also the man behind a cutting-edge lawsuit that could change the way businesses use the Internet.

A jury at the federal courthouse in Greenbelt will decide as soon as Thursday whether Wagner, 48, is a bona fide Internet service provider battling alleged spammers who clog his in-boxes with offers for everything from coffee to appliances. Wagner’s detractors say he’s taking advantage of the law, intentionally seeking out spam in order to sue for $1,000 for each piece of deceptive e-mail.

He’s already taken in more than $1 million from spammers.

Legal experts think that it’s one of the first jury trials in a federal civil case brought by a private citizen and not the government, and it has implications for how the nation’s patchwork of anti-spam laws are used in court.

Eric Sinrod, a San Francisco lawyer who focuses on Internet issues, said these cases are unusual because it is difficult to ferret out who is initiating the spam and because e-mail filters have gotten better at blocking unsolicited commercial messages.

“Anti-spam laws can be relatively harsh if you can prove actual violations,” Sinrod said. “On the other hand, if it looks like there is some sort of scheme, where they are trying to manufacture a lawsuit, hopefully a jury in such a case would see through that.”

Wagner, a graduate of Georgetown University with a master’s degree from MIT, testified last week that he has a penchant for “assembling fast machines.” His lead attorney described him as a “bit of computer geek,” and he spoke so quickly and in such highly technical terms on the witness stand that U.S. District Judge Peter J. Messitte repeatedly told him to slow down.

Wagner started setting up specialized computers at his parents’ home and created Beyond Systems Inc. in 1996, in part to run tests for his technology consulting business. He created e-mail addresses for friends and family, hosted community e-mail groups and helped neighborhood nonprofit groups use the Internet.

Wagner has testified that he has had just two-dozen paying clients in the past decade, including his father and his housemates on R Street in Northwest.

But Wagner’s e-mail in-boxes have amassed a huge collection of unsolicited junk mail that he has used to successfully sue spammers in a series of cases for “litigation proceeds” of $1 million between 2005 and 2011, according to his statements in preparation for trial.

“There’s an intellectual curiosity and an anger that it’s going unpunished,” one of his attorneys, Mike Rothman, said of the spam. “These are public-interest lawsuits to find out where all this garbage is coming from.”

In Wagner’s complaint, he identifies hundreds of e-mail solicitations from the coffee company Gevalia, which he says were sent by a single spammer under multiple domain names “to mask the true identity of the senders, and to prevent complaining parties from contacting them.”

Other Gevalia e-mails, the complaint alleges, contain false or misleading information. The subject line in one message, for instance, says, “ ‘Free Stainless Steel Coffeemaker & 2 Travel Mugs from Gevalia’ ” when a purchase is required, according to the complaint.

Gevalia is owned by Kraft Foods, one of the defendants in the case. The other defendant is the advertising affiliate company, Connexus Corp., which the complaint says Kraft used to send Gevalia e-mails from California to Maryland.

A Kraft spokesman said in a statement that Gevalia’s electronic marketing complies with all state and federal laws. “We believe the plaintiff’s lawsuit is without merit.”

Wagner’s lawsuit seeks more than $12 million from Kraft under anti-spam laws in both states and alleges that thousands of e-mails sent between 2005 and 2008 have harmed Wagner’s business by “requiring the application of time, money and technological resources to handle the spam.”

Attorneys for Kraft and Connexus have argued in court and in legal documents that Wagner’s only business is intentionally collecting such e-mails by “deploying ‘spam traps’ to capture and save alleged ‘spam’ ” to use as fodder for lawsuits.

Tens of thousands of e-mails Wagner is now suing over, the attorneys say, were intentionally sent to Wagner by his brother in California. Joe Wagner has filed a series of his own anti-spam lawsuits from the Internet service provider he was running while working on a doctorate in mechanical engineering at Stanford University.

In opening statements, Connexus attorney J. Douglas Baldridge compared Wagner to a person who intentionally dives in front of a bus, knowing he is going to get hit, and then sues the driver. Baldridge asked the jury: “Are you going to allow those people that do everything they can to receive this spam, knowing they’re getting it, to make lots of money off of it — over a million bucks?”

Rothman said there is nothing unusual about what Wagner is doing.

“It’s like blaming a homeowner for setting a mousetrap,” he said.

More than half the states and the federal government have laws restricting commercial e-mail. Maryland’s law, passed in 2002, allows individuals to sue for $500 for each piece of misleading e-mail and $1,000 for Internet service providers.

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