Edgar Jimenez Lugo, who just turned 15, helped murder four men and kidnap three others last year at the service of a major criminal band, Judge Jose Luis Jaimes ruled.

The teen will serve his sentence at a youth prison outside the city of Cuernavaca, about 50 miles south of Mexico City.

Jimenez was arrested by army troops last December as he attempted to board a flight for Tijuana en route to his mother's home in San Diego, Calif. Paraded before the new media by soldiers, the boy confessed to the murders and other crimes.

"I slit their throats," Jimenez said in response to a reporter's question, shocking a Mexican public already hardened by years of gangland fighting that's claimed some 40,000 lives. The boy said he started his career as a killer at the age of 11.

Sisters also face trial

The public confession was inadmissible in the trial, which began on July 18. Instead, state prosecutors called 42 witnesses in the closed-door oral trial, including several of those Jimenez was accused of kidnapping.

The boy's court appointed attorneys did not call a single witness, and the judge ruled other evidence presented by them was invalid.

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Jimenez and other under­aged accomplices worked as enforcers for the Beltran Leyva narcotics smuggling syndicate in the Cuernavaca area. After Mexican marines killed the gang's boss, Arturo Beltran Leyva, it fell into internal warfare through much of last year. The result was hundreds of dead in and near Cuernavaca.

Jimenez was tried only for the killing of four men whose bodies were hanging from a busy highway overpass. In addition, he was convicted of narcotics trafficking, weapons possession and kidnapping, the state prosecutors office said in a statement.

Two older sisters arrested along with Jimenez will be tried as adults for similar crimes. They face decades in prison.

But under judicial reforms enacted two years ago, Morelos state sets a maximum sentence of three years for offenders aged 12 to 15. Older minors can go to prison for five years, and those younger than 12 can't be tried at all.

Born in California

With credit for time served, Jimenez could be released in December 2013, according to court officials. Because he faces no U.S. charges, the teen will be free to move north of the border upon release.

El Ponchis and his siblings were brought to Cuernavaca by their paternal grandmother shortly after Edgar was born in San Diego. The children were taken by child welfare authorities after testing reportedly found cocaine in Edgar's bloodstream. Both parents were addicted to crack cocaine and had frequent brushes with the law.

After his grandmother's death and then frequent run-ins with teachers, the boy was allowed to drop out of school after the third grade. His street life began then.

The Jimenez siblings were said to work directly for Julio "Blackie" Radilla, a local Beltran Leyva lieutenant who was arrested this spring for the late March murders of seven innocent people whose bodies were found stuffed into a compact car near Cuer­navaca.

Among those victims was the 24-year-old son of poet Javier Silicia, who in June led a protest caravan across northern Mexico calling for an end to the government's war on gangsters.

dudley.althaus@chron.com