SAN FRANCISCO >> The undercover FBI agent at the center of an organized crime investigation in San Francisco’s Chinatown testified Tuesday that he posed as a vulgar, racist member of an East Coast crime syndicate that was involved in illegal sports betting and marijuana cultivation and needed help laundering money.

The character he played for more than three years was not someone he would like, the agent, testifying under the pseudonym "David Jordan," to protect his identity, said during his first hour on the stand in the murder and racketeering trial of Raymond "Shrimp Boy" Chow. He is expected to resume his testimony on Wednesday morning.

"He was abhorrent to say the least," the agent said. "Unsavory, just amoral."

The judge overseeing Chow’s trial did not allow reporters or members of the public in the courtroom during the agent’s testimony to protect his identity. Only the top of the agent’s head was visible on a screen in a separate room where the proceedings were broadcast.

The agent said he developed a false back story that included a grandfather whose Italian name was changed to ‘Jordan’ when he emigrated from Italy to the United States and a dummy company, Madison International, which his family used to launder money.

Jordan spent hours with Chow and people connected to him at fancy restaurants, recording many of their conversations as he built a case that would ultimately lead to criminal charges against Chow and more than two dozen others and the conviction of a state senator. Former state Sen. Leland Yee pleaded guilty to racketeering in July.

Federal prosecutors say Chow took over a Chinese fraternal group with criminal ties after having its previous leader murdered and ran a racketeering enterprise that engaged in drug trafficking, money laundering and the sale of stolen cigarettes and alcohol.

They say Chow introduced the agent to people who helped the agent launder money and engage in other crimes and accepted money for the introductions. Chow’s attorneys say the agent instigated the crimes for which people were later arrested, and forced money on Chow, often when he was drunk.

One of the Chow’s associates during a 2011 meeting in Las Vegas put a gun and bag of cocaine on the table before they began talking about buying drugs and whether the associate could trust the agent, the agent said. He said he was "incredibly frightened" and tried to deescalate the situation.

"If I didn’t compromise the case that would be good," he said he thought to himself at the time. "But my safety and going home to my family was certainly more important."