A 27-year-old Filipino national was sentenced Tuesday to seven years in prison for smuggling military-grade weapons into the U.S., in a case that offered a rare, unflattering look inside an undercover FBI operation.

During the two-year case, one FBI agent was forced to answer questions about thousands in taxpayer dollars spent at brothels, and another was accused of paying for sex with a prostitute while on the job in the Philippines.

On Tuesday, it was Sergio Santiago Syjuco who was in the hot seat. U.S. District Judge R. Gary Klausner handed down the sentence for his conviction last March on illegally importing weapons including machine guns, sniper rifles, grenade and mortar launchers, and ballistic vests, along with two other defendants. The weapons arrived in a container marked "furniture and household" items at the Long Beach port in 2011.

"You screwed up, no question about it, this is very serious," the judge told Syjuco, adding that the defendant committed a "very dangerous offense" with potential for great harm.

Klausner did not address arguments by Syjuco's attorney, Deputy Federal Public Defender John Littrell, who contended that the case had been "created by the government from beginning to end." Littrell argued that a charismatic undercover FBI agent had "induced" a naive, susceptible Syjuco into procuring weapons, plying him with alcohol and prostitutes.

"He tried to puff himself into, or appear to be, the type of weapons trafficker Chuck Ro was looking for," he argued, referring to Special Agent Charles Ro. "This offense never would have happened were it not for inducement by the government."

Assistant U.S. Atty. Kim Dammers dismissed Littrell's allegations, saying that Syjuco was fully aware of where the weapons were going and that they were intended for nefarious purposes. The agent, posing as an international arms broker, told Syjuco and the other defendants that he worked for the Mexican drug cartels and the Mexican Mafia.

"This is not a case of these poor guys, they were entrapped," she told the judge, noting that Syjuco and the others flew to the U.S. believing that they were to take part in another weapons deal. "Mr. Syjuco engaged in this weapons trafficking solely for the purpose of monetary gain."

In the audience at Syjuco's sentencing was one of the jurors who voted to convict him, Bryan Croft. In a sworn declaration submitted by defense attorneys, Croft wrote that he was "disappointed" and "shocked" by the FBI's tactics.

"I don't think they ever would have been shipping weapons to the United States if it hadn't been for the agents throwing money, women and booze at them," Croft wrote.

Klausner said he would not take into consideration one juror's opinion and said the law leaves sentencing up to the judge, not the jury.

Ro, the agent, took the stand in early 2013 to testify about the operation in the Philippines in a lengthy hearing in which defense attorneys alleged "outrageous government misconduct." District Judge Robert Timlin ruled at the conclusion of the hearing that though the venues where the agent met with the defendants were "unsavory," their acts were not "shocking enough to warrant dismissal."

Special Agent Marc Napolitano testified that he had sex with a karaoke club employee and gave her about $80, but he said the money was for her ailing father.

victoria.kim@latimes.com