The lawsuit, filed in U.S. District Court in San Jose, accuses the multinational high-tech giant of breaking U.S. wiretap laws by scanning all emails to target Gmail users for advertising.
Gmail is a free, advertising-supported email service. The service also automatically scans all emails to filter spam.
The class action, filed by California residents in May, asserts Google "unlawfully opens up, reads and acquires the content of people's private email messages."
It quotes Google Executive Chairman Eric Schmidt as saying in October 2010, "Google policy is to get right up to the creepy line and not cross it."
It quotes him as saying in December 2009, "If you have something that you don't want anyone to know, maybe you shouldn't be doing it in the first place."
And it quotes him as saying in October 2010: "We know where you are. We know where you've been. We can more or less know what you're thinking about."
"Unbeknownst to millions of people, on a daily basis and for years, Google has systematically and intentionally crossed the 'creepy line' to read private email messages containing information 'you don't want anyone to know,' and to acquire, collect, or 'mine' valuable information from that mail," the class-action lawsuit alleges.
"Google has one intended purpose for this systematic practice of reading private messages and collecting the data therein: to know and profit from what 'you're thinking about,'" says the complaint, which can be found at tinyurl.com/UPI-Class-Action-Lawsuit.
In its motion to dismiss the case, found at tinyurl.com/UPI-Google-Motion-to-Dismiss, Google says the plaintiffs seek "to criminalize ordinary business practices" Google has used since Gmail was introduced in 2004.
"All users of email necessarily give implied consent to the automated processing of their emails," Google argues.
"Just as a sender of a letter to a business colleague cannot be surprised that the recipient's assistant opens the letter, people who use Web-based email today cannot be surprised if their communications are processed by the recipient's ECS [electronic communications services] provider in the course of delivery," Google says.
The Mountain View, Calif., company cites a 1979 U.S. Supreme Court decision in Smith vs. Maryland, in which the court said, "A person has no legitimate expectation of privacy in information he voluntarily turns over to third parties."
John Simpson, privacy project director of the non-profit Consumer Watchdog advocacy group, called Google's court filing a "stunning admission."
"Google has finally admitted they don't respect privacy," he said in a statement.
"People should take them at their word," he said. "If you care about your email correspondents' privacy, don't use Gmail."
Simpson, whose statement can be seen at tinyurl.com/UPI-Consumer-Watchdog, also said Google's analogy about mailing a letter to a business colleague was "wrong-headed."
"Sending an email is like giving a letter to the post office," he said. "I expect the post office to deliver the letter based on the address written on the envelope. I don't expect the mail carrier to open my letter and read it.
"Similarly, when I send an email, I expect it to be delivered to the intended recipient with a Gmail account based on the email address" without being intercepted by Google and read, he said.
Google said in a statement late Wednesday, "We take our users' privacy and security very seriously; recent reports claiming otherwise are simply untrue.
"We have built industry-leading security and privacy features into Gmail -- and no matter who sends an email to a Gmail user, those protections apply," Google said.
The case comes as Google seeks to allay privacy fears stemming from its agreement, in common with other major technology companies, to comply with U.S. national security data requests.
Google says it has provided information for the National Security Agency only when legally compelled. It called on U.S. Attorney General Eric Holder and FBI Director Robert Mueller last month to lift restrictions so it can publicly explain the scope of the government requests.
Notable deaths of 2014 [PHOTOS]