A former Quinn Emanuel Urquhart & Sullivan litigator has launched his own firm, just six months after opening a San Franciso office for Greenberg Traurig, reports The Recorder.

Ex-Quinn Emanuel partner Samuel Shepherd announced the launch of the new practice, Sam Shepherd Law, last week.

On his move to Greenberg in February this year, Shepherd said: "I don't think we looked at things hard enough or talked to the right people."

"I don't think we did a good enough job vetting it, both Greenberg and me," he said. "We should have been more thorough. I might not have gone in the first place."

Shepherd said that his practice is one-third large plaintiffs contingency work, which Greenberg did not want to be on the plaintiffs side of. There were a number of patent, intellectual property and consumer fraud class actions that he had been planning to take to trial, but couldn't at Greenberg because of business conflicts.

Kenneth Steinthal, who has taken over as the sole office managing partner of Greenberg's San Francisco office, said the firm did not ask Shepherd to leave.

"Sammy wanted to pursue certain kinds of cases he couldn't pursue at a firm the size of Greenberg Traurig," Steinthal said. "He realised after six or seven months here that he could better pursue those kinds of cases on his own."

Steinthal downplayed any impact on the firm. "Do I wish Sammy was still here? Yes, in the sense that he's a positive person, but this office is not going to skip a beat," he said. "Things like this happen in the evolution of a law firm."

Steinthal opened the San Francisco office with Shepherd and co-managed it for the past few months. In the spring the firm added three lawyers, including partner Scott Lawson, a former Quinn Emanuel lawyer and friend of Shepherd's.

Asked about its vetting process of lateral partners, Greenberg said through a spokeswoman that the firm is not re-examining its model as a result. "Our hiring system has served us well over the years, but Sam had some opportunities that we could not take," the spokeswoman said.

The Recorder is a US affiliate title of Legal Week.