SAN FRANCISCO — The long-awaited legal showdown between Raymond “Shrimp Boy” Chow and the federal government got underway Monday as a federal jury was presented with starkly differing portraits of the sweeping racketeering charges against him.

Dressed in a dark suit jacket, tie and sweater vest, the reputed Asian organized crime boss listened intently as federal prosecutors portrayed him as the architect of a violent crime wave in San Francisco’s Chinatown.

“Like planets revolving around the sun, this case is about the man at the center of this criminal underworld universe,” assistant U.S. attorney Waqar Hasib told the jury.

The trial, expected to stretch until at least late January, will decide racketeering charges against Chow ranging from drug trafficking and money laundering to murder — and also serve as a referendum on the government’s five-year undercover sting operation, which relied on wiretaps, informants, bags of cash and booze-filled meetings in fancy hotels and restaurants to snag the FBI’s quarry, including former state Sen. Leland Yee.

J. Tony Serra, Chow’s flamboyant defense lawyer, immediately jumped on the government’s case in his opening salvo to the jury, promising that Chow would take the unusual step of testifying in his own defense during the trial. Serra put up video slides of Chow’s conversations with undercover FBI operatives, including instances of trying to resist envelopes of cash, and showed jurors the FBI’s multimillion dollar tab for its five-year probe, from $250 shots of expensive whiskey to Las Vegas resorts.

“Understand there is two sides to this story,” Serra boomed. “My client didn’t participate in any criminal act. My client did nothing.”

Federal prosecutors depict Chow as a violent gang leader with a long history of overseeing Chinatown’s crime scene. Chow’s lawyers, however, say he was a reformed criminal who turned straight only to be framed by federal agents trying to justify one of the longest and most expensive undercover probes in recent Bay Area history.

With Yee and other key defendants in the case already pleading guilty to racketeering charges, the trial may be the public’s only full glimpse of the government’s operation.

In a sweeping federal indictment alleging dozens of crimes, prosecutors portray Chow as the leader, or “Dragonhead,” of an Asian organization called the Ghee Kung Tong that law enforcement agents say was involved in drug and gun trafficking and money laundering, as well as trafficking in stolen booze and cigarettes. Charges added to the case in October also now link Chow to the murders of at least two alleged gang rivals, one gunned down in San Francisco in 2006 and the other found dead with his wife in Mendocino County two years ago.

In fact, Hasib, the federal prosecutor, began his remarks to the jury describing the February 2006 slaying of Allan Leung, Chow’s predecessor as head of the Ghee Kung Tong. “This was a coldblooded, gangland-style hit, something straight out of “The Godfather,’ ” Hasib told the courtroom. “Ordered by that man over there, Raymond Chow.”

During the course of the undercover probe, Chow allegedly accepted thousands of dollars in cash for a variety of crimes from FBI agents posing as businessmen and gangsters, according to court papers. Federal prosecutors told the jury that undercover conversations show that Chow, despite occasional protestations, frequently then accepted money to carry out crimes.

The 55-year-old Chow previously served federal prison time for racketeering and other crimes. He was sentenced to 24 years in federal prison in 2000, but served only three years after cooperating in the government’s case against another reputed Asian organized crime figure.

Defense lawyers plan to put the government itself on trial, particularly the lead undercover FBI agent, who met repeatedly with Chow, plying him with drinks and handing him envelopes of cash in posh spots such as the Hotel Nikko in San Francisco. The agent is only identified as “Dave,” but his role is expected to be central in the trial.

But Hasib told the jury that the undercover agent, who went by “David Jordan” and posed as an East Coast Mafia businessman, ingratiated himself to Chow and got him to “drop his cover.”

“I expect David Jordan to be on the stand a lot,” Hasib said.

Serra, however, refuted the prosecution’s charge that Chow was involved in any murders, telling the jury that the government is relying on career criminals trying to get better deals for their cooperation. And he blasted the government for trying to lure Chow into crimes while he was trying to go straight.

“I invite you to dislike that,” Serra said of the undercover operation. “It should trouble you. This evidence was a disgrace.”

The trial is unlikely to delve much into the political corruption allegations against Yee, who was charged with accepting bribes in exchange for political favors. But it is expected to touch on the origins of the investigation, which only stumbled upon Yee as the FBI probe into Chow’s dealings connected the ex-legislator with a number of figures, including San Francisco political consultant Keith Jackson, who also has pleaded guilty to racketeering.

The government and defense team did not mention Yee in opening statements to the jury.

Howard Mintz covers legal affairs. Contact him at 408-286-0236 or follow him at Twitter.com/hmintz