San Francisco's biggest gang trial in years is heading to a federal court jury today after attorneys offered a final round of competing narratives of organized mayhem on the city's streets and unreliable accusations by government-paid informants.

The Mission District unit of the gang known as MS-13 "waged war against rival gang members" and "ended up spilling a lot of blood on the streets of San Francisco," Assistant U.S. Attorney Wilson Leung told the jury last week during seven days of closing arguments, due to end today.

In more than four months of testimony in U.S. District Court, the prosecution sought to portray the seven defendants as principals of a heavily armed organization that controlled its territory through fear and intimidation.

All seven face up to life in prison if convicted of a racketeering conspiracy that includes four 2008 murders.

MS-13, or Mara Salvatrucha, originated in El Salvador. Members are initiated by "jumping in," a beating that lasts 13 seconds. Then, according to prosecutors, they rise in the ranks by committing acts of violence.

Eighteen others indicted in 2008 have pleaded guilty, including two men who were sentenced to 20 years each for the fatal stabbing of 14-year-old Ivan Miranda in the Excelsior district in July 2008, and two others who await trial for a slaying outside the Daly City BART Station in February 2009.

Additional guilty pleas have come from six men who are awaiting sentencing after testifying for the prosecution. Their credibility is a critical issue in the case.

The witnesses provided inside accounts, supported by secretly recorded conversations, of attacks and plots in which they - and, allegedly, the defendants - took part.

Defense lawyers focused on inconsistencies in the witnesses' statements to federal agents and the jury. They said the six men, who were paid and promised reduced sentences in exchange for their cooperation, could not be trusted.

One witness, Jaime Martinez, "described how he was cooperating and would sell out his own brother to save his skin," said Lupe Martinez, lawyer for Angel Guevara, whom prosecutors described as a leader of MS-13's "clique" at 20th and Mission streets.

Mark Rosenbush, lawyer for defendant Moris Flores, said allegations that Flores had taken part in or ordered three separate shootings were based entirely on Jaime Martinez's uncorroborated testimony.

Martinez "is a liar, he is manipulative and deceptive," Rosenbush told the jury.

Prosecutors said the informants' testimony was corroborated by other evidence, including cell phone records tracking the defendants' movements after fatal shootings as well as their own clandestinely taped statements.

"No one is asking you to like the government's witnesses, but fairly and rationally evaluate their evidence," Leung, the prosecutor, told the jury.

The central charge in the case is racketeering, a conspiracy in a criminal enterprise that includes drug dealing, assaults and murders. The murder victims include Ernad Joldic and Philip Ng, described by prosecutors as ordinary people who happened to be wearing a rival gang's color, red, in the wrong neighborhood one day in March 2008.

Another man, Juan Rodriguez, was killed in a revenge slaying in May 2008, and Armando Estrada, a seller of fake documents, was shot in broad daylight in July 2008 for refusing to pay "taxes" to MS-13 in its territory, prosecutors said. They said a witness saw defendant Guillermo Herrera take off his bandanna and laugh after shooting Estrada.

Besides Guevara, Flores and Herrera, the defendants are Marvin Carcamo, Erick Lopez, Jonathan Cruz Ramirez and Walter Cruz-Zavala.