The power of anonymous comments—and the liability of those who make them—is at the heart of a possible legal battle embroiling PubPeer, an online forum launched in October 2012 for anonymous, postpublication peer review. A researcher who claims that comments on PubPeer caused him to lose a tenured faculty job offer now intends to press legal charges against the person or people behind these posts—provided he can uncover their identities, his lawyer says.

The issue first came to light in August, when PubPeer’s (anonymous) moderators announced that the site had received a “legal threat.” Today, they revealed that the scientist involved is Fazlul Sarkar, a cancer researcher at Wayne State University in Detroit, Michigan. Sarkar, an author on more than 500 papers and principal investigator for more than $1,227,000 in active grants from the U.S. National Institutes of Health, has, like many scientists, had his work scrutinized on PubPeer. More than 50 papers on which he is an author have received at least one comment from PubPeer users, many of whom point out potential inconsistencies in the papers’ figures, such as perceived similarities between images that are supposed to depict different experiments.

Recently, PubPeer was contacted about those comments by Nicholas Roumel, an attorney at Nacht, Roumel, Salvatore, Blanchard & Walker P.C. in Ann Arbor, Michigan, who represents Sarkar and spoke to ScienceInsider on his behalf. On 9 June, the University of Mississippi Medical Center announced that Sarkar would join the faculty in its school of pharmacy. Records from a meeting of the Mississippi Board of Trustees of State Institutions of Higher Learning note that he was offered a tenured position and a salary of $350,000 per year, effective 1 July.

But on 19 June, Roumel says, Sarkar got a letter from the University of Mississippi revoking its offer. Science has not seen the letter, but Romel says that in his view, “it made it crystal clear the PubPeer postings were the reason they were rescinding the job offer.” A representative for the University of Mississippi declined to comment on the case, citing prospective employees’ confidentiality.

According to Roumel, Wayne State allowed Sarkar to keep the position he had formally resigned but revoked his tenure. The events have “had a devastating effect on his career,” Roumel says. A representative of Wayne State confirmed that Sarkar is employed there but gave no details about any change in his status.

Roumel says that because Sarkar suspects the person or persons who posted some of the PubPeer comments also circulated them to the University of Mississippi, as well as to colleagues in his department at Wayne State, he wants to find out their identities and file suit against them. One possible charge is defamation, Roumel says, because he believes several comments—some now removed by PubPeer’s moderators—stray from the facts to insinuate deliberate misconduct, in violation of PubPeer’s posting guidelines. Roumel has exchanged letters with PubPeer requesting the identity of the commenters, but no suits or request for a subpoena have been filed.

PubPeer argues that researchers should defend their papers against online comments without resorting to legal action. “Authors have every opportunity to respond directly to any comments on PubPeer they feel are unjustified,” an anonymous PubPeer contact told ScienceInsider in an e-mail.

Roumel’s response is that his client has no responsibility to critics who refuse to put a name to their accusations. “I don’t think he has any obligation to provide the data [behind the papers called into question] to anyone other than a journal,” he says.

PubPeer’s own liability is a separate issue. If the site merely provided a forum for the comments and did not contribute to their content, as its moderators maintain, they would be immune from libel actions under a section of the Telecommunications Act of 1996, says Nicholas Jollymore, a libel lawyer at Jollymore Law Office P.C. in San Francisco, California, who represents PubPeer. But the effort to identify the commenters may involve a subpoena to PubPeer for information about it users, Roumel says.

And although those who post comments have a right to anonymity under the First Amendment, “it’s by no means an absolute right,” says Alexander Abdo, a lawyer with the American Civil Liberties Union (ACLU) in New York City. They can lose this protection if there is a strong case of wrongdoing against them. “Whoever is trying to unmask someone needs to show that there is some likelihood of success of their claim,” Abdo says. He says the ACLU would work with Jollymore to defend PubPeer should Sarkar go forward with a lawsuit or subpoena.

It’s not clear how much information a subpoena would yield. Users can create a PubPeer account using their e-mail address at an academic or research institution, but others submit “unregistered” comments through the site’s moderators. PubPeer may have names and e-mails for registered posters, but only IP addresses for the others. An Internet service provider may be able to look up who accesses the Internet from an IP address at a given time, Abdo says, but there are also ways to conceal one’s identity from such a search. Asked about possible wrongdoing by the PubPeer community, the moderators replied, “We will do everything possible to protect our users.”