People waiting to cross from Mexico into the United States at the San Ysidro port of entry, November 2013, in San Diego. John Moore/Getty Images

Cruz’s story is increasingly common. From 2008 through 2013, 978 minors were caught by the CBP and charged with drug trafficking in the San Diego sector alone. (Borderwide statistics aren’t readily available.) That figure has leveled out but remains high compared with the rate of juvenile drug trafficking prior to 2008.

The latest statistics related to drugs seizures in San Diego show that marijuana busts dropped from 121 cases in 2010 to just 36 in 2012. But methamphetamine and cocaine seizures have both doubled.

To the east, in the Tucson, Ariz., sector, the number of juvenile apprehensions has also increased. In 2012, 244 minors reportedly faced drug-smuggling charges, double the number from 2011. Smugglers recruit minors because they are more easily swayed by promises of cash, cellphones and clothes. A typical cash payoff is $100 to $200. Minors are also sought out because they are more likely to recruit their friends and peers.

It’s not uncommon for high school students from San Diego County to cross into Mexico to party or visit family, particularly since the legal drinking age south of the border is 18. Agents say that kids are approached at the mall, in their neighborhoods, or at parties. Drug mules as young as 12 have been caught at the border.

An estimated 50,000 vehicles and 25,000 pedestrians flow north from Tijuana each day. The volume of traffic makes catching smugglers difficult, Millie Jones, assistant special agent with the Department of Homeland Security (DHS), said, “The system isn’t set up to check every person. The average person wants to believe that kids are innocent and they’re not going to be the ones smuggling narcotics. The cartels see that.”

Often teens are assured that if they are caught smuggling drugs, they won’t face serious consequences because of their age. That is only partly true.

“By and large, there is a huge gap in sentencing for juveniles and adults,” said San Diego criminal defense lawyer Jeremy Warren, who has represented numerous juvenile offenders. “Juvenile sentencing is considered treatment and rehabilitation, and the punishments are generally much shorter, from probation to a few months in jail, at least in California.”

Adults, he said, can face years in prison for the same conduct. “It seems pretty arbitrary, but for the same crime — say, driving across the border in a car with a few pounds of cocaine inside — a 17-year-old might get (a sentence of) time served in juvenile court after a few weeks, while an 18-year-old might get three or four years in federal prison.”

For those 18 and up, punishment ranges from five to 20 years in prison, with fines that can top $5,000. The sentence depends on the type and quantity of drugs involved and whether the accused is tried in state or federal court. Many adult mules get three or four years, Warren said.

Penalties for mules under 18 range from probation to up to 15 months in a juvenile work camp.

Offenders convicted of aggravated felony crimes, like drug trafficking, who are noncitizens — adults and juveniles alike — are automatically deported for life after serving their sentences. According to statistics obtained from Immigration and Customs Enforcement via a Freedom of Information Act request, more than 65,500 immigrants were deported from 2007 to 2009 after aggravated felony convictions.

On one particular day in 2008, five teenagers were arrested in 24 hours, said Jones. She said it was a wake-up call. Some of the kids were apprehended at the same port of entry where Cruz drank liquid meth, others at Calexico to the east. “All of them had hard narcotics, cocaine or meth strapped to their bodies,” she said.

After seeing a 16 percent surge from 2008 to 2009 in the number of minors caught trying to smuggle drugs across the border, the DHS began an outreach program, organizing annual presentations in schools. The program now includes 38 elementary, middle and high schools in southern San Diego and features testimonies from agents from Immigration and Customs Enforcement, DHS Special Investigations, the U.S. Attorney’s office, the CBP and the San Diego Police Department.