David Martosko—the outgoing executive editor of the conservative Daily Caller and a prominent defender of the news site’s disputed claim that Sen. Bob Menendez (D-N.J.) paid two women for sex in the Dominican Republic—admitted in a court document obtained by Mother Jones that he used a fake Facebook profile to pose as a “dope-smoking commie” in order to gather information on animal rights activists. The admission came in a May 2011 deposition Martosko gave under oath as part of a defamation case against him and his former employer, Berman and Company, a PR shop that specializes in combating progressive activists who target corporations.

Before Daily Caller Editor in Chief Tucker Carlson hired him in 2011—a controversial choice given Martosko’s previous arrests and lack of experience in journalism—Martosko spent a decade working for Richard Berman, a longtime PR operative behind a number of industry-backed campaigns. At Berman and Company, Martosko served as the director of research for the Center for Consumer Freedom, a Berman-run nonprofit that opposes new laws on food and beverages. CCF, which is funded by the food and beverage industry, runs Humane Watch, a website that posts derogatory information about the Humane Society of the United States. Martosko was the site’s “founding editor.” CCF also operates Activist Cash, a website that compiles biographical information on groups and individuals that engage in “anti-consumer activism.”

In the 2011 deposition, Martosko acknowledged he used a Facebook account under the name of “Gregory Davis” (later changed to “Preston Davis”) to obtain information about animal rights activists. (You can read the full deposition here.) Here’s the exchange:

Q: Okay. Well, have you ever used a Facebook name that was not your own? Martosko: Yes. Q: And what name was that? Martosko: I believe it was Preston Davis. Q: And was that the only Facebook name you’ve used? Martosko: Other than my own? Q: Other than your own. Martosko: Yes. Q: Okay. What about Gregory Davis or Greg Davis? Martosko: Ah. That was—I think that was originally—forgive me. That was originally the name of the same account, and then that name was changed. Q: Okay. And you had used that to friend activists, I guess that you were wanting to learn more information about; is that correct? Martosko: That’s correct.

Martosko’s aim was to connect with animal rights activists as Facebook friends to collect intelligence on their plans and activities. Later in the deposition, Martosko said that he didn’t remember how many activists he friended using the Davis account.

Although animal rights activists had long suspected that Martosko was behind the Davis Facebook account, the deposition marked the first time he acknowledged the scheme. Martosko appears to have created the Facebook account in 2009, according to an exhaustive 2011 analysis of Davis’ online activities published by HumaneWatch.info, a website created to track CCF’s work. The profile for this account, according to the site, was “a two-dimensional caricature of a vegan activist, with a few superficially liberal interests and a political affiliation listed as ‘dope-smoking commie.'”

As Gregory Davis, Martosko posted about stereotypically lefty, vegan, and animal activist subjects, such as “living in a wood hut” and hanging out with his “freegan crew,” and friended progressive activists and groups such as PETA, the Humane Society of the United States, Mercy for Animals, Sea Shepherd, and Stop Humane Watch, a group that aimed to monitor and push back on Martosko’s outfit. Many of the individuals Gregory Davis friended were later profiled on a CCF website devoted to monitoring animal rights activists.

“Davis wanted people to think he was a real extreme animal rights advocate or like a vegan abolitionist. He kind of invented a cover story for himself,” one of the women who moderated the Stop Humane Watch Facebook page in 2010 told Mother Jones. (She asked that she not be identified, citing job concerns.) “I didn’t think much of it at the time,” she noted. “When people posted abolitionist or extreme stuff, we dealt with it. We weren’t about doing away with farms altogether; we were about changing the practices.” She recalled a particular incident in May 2010 when Gregory Davis posted a comment advocating violent action against Conklin Dairy—an Ohio farm that was the target of protests after animal rights campaigners released a video of a worker abusing livestock.

“He was trying to rile up people to go to this protest,” the moderator said. The post was taken down, as Stop Humane Watch did not want be seen as encouraging violent acts. Asked about the Conklin Dairy incident in the deposition, Martosko said, “I don’t recall doing that.” But he would not absolutely deny he did so.

Over time, Gregory Davis began posting out-of-character comments, including criticism of the Humane Society of the United States and a defense of Martosko in threads about Martosko’s personal life and CCF’s work. Consequently, activists grew leery. “He kind of betrayed himself,” the moderator said. “The more he talked, the more he showed he was inconsistent.” In late 2010, Stop Humane Watch began warning people not to friend Gregory Davis. Around that the time, Kevin Fulton, a farmer from Nebraska active in animal rights work, began to suspect Gregory Davis was actually Martosko. “I just went on a hunch, and I was right. The old farm boy gut instinct,” Fulton said. “At first the other guys [in the group] said, ‘I don’t know…’ I said, ‘I’m telling you, I think it’s Martosko.'”

Soon thereafter, Martosko changed the name on the account to “Preston G. Davis.” Following up on Fulton’s hunch, the activists who run HumaneWatch.info were able to trace the IP address for the computer Gregory/Preston Davis was using to Berman and Company’s office in Washington, DC.

The Facebook profiles don’t appear to be first time Martosko used the Gregory Davis persona online. Mother Jones was able to find comments dating back to 2001 on anarchist and animal rights web forums from a commenter using the email address linked to the Facebook profile. In one instance, Davis posted a USA Today column by Martosko’s boss, Richard Berman, and solicited activists’ “thoughts.”

Martosko acknowledged his use of the Davis account as part of a defamation suit regarding an ad CCF placed in the New York Times in December 2008. The ad claimed that the Humane Society of the United States was “helping a terrorist group raise money” because the group’s vice president was slated to appear at a fundraiser for another animal rights group, the Humane League of Philadelphia, which CCF claimed was started by affiliates of an organization whose members had been imprisoned for violating the Animal Enterprise Protection Act. The Humane League of Philadelphia sued Berman and Company, the Center for Consumer Freedom, Richard Berman, David Martosko, and the New York Times. Last month, a judge in the New York State Supreme Court agreed to dismiss the defamation suit against the Times, but the case against Berman and Martosko is moving ahead. (Read the judge’s decision here.)

Martosko, who announced recently that he is leaving the Caller to become the US political editor for the UK-based Daily Mail, has been involved in several controversies during his short career in journalism. Most recently, Martosko defended the Daily Caller‘s reporting on two Dominican women who claimed that they were paid to have sex with Menendez—allegations Menendez has repeatedly denied. Earlier this month, the Washington Post reported that one of the women came forward to say that she had in fact never met Menendez and had been paid to make false allegations. (The Caller claims that she was not one of the two women that it had interviewed.)

Martosko also drew negative press in September 2011 when he insisted that a Daily Caller report claiming the Environmental Protection Agency planned to hire 230,000 employees to enforce greenhouse gas regulations was legitimate, even as numerous outlets criticized the Daily Caller for inaccurate reporting.

At the Caller, Martosko has not always disclosed his previous work with Berman and Company. In a piece last August criticizing a teachers’ union, Martosko quoted Berman without mentioning that he used to work for him. In another article, Martosko cited a report obtained by CCF without saying that he used to work there.

Carlson has defended his decision to hire Martosko from Berman and Company, despite Martosko’s lack of journalism experience. “I hired Martosko because he’s smart and aggressive, the two qualities I care about most in new hires,” Carlson told the Washingtonian recently. “You can teach journalism. Despite lots of effort to pretend otherwise, it’s not that complicated. Look at the people who do it.”

Carlson says he’s not concerned about Martosko’s admission that he used a fake identity as a PR operative to infiltrate and undermine the animal rights movement. “I watched carefully everything David did, and I was satisfied that everything was completely aboveboard and honest from the second he got here,” Carlson told Mother Jones. Martosko did not respond to a request for comment.

UPDATE: Martosko sent a comment, by email, on Friday afternoon: