Before Operation Streamline, as the program is known, most Mexican nationals caught at the border were fingerprinted and returned to Mexico without criminal charges. Since 2005, people other than Mexicans are generally held until removed.
In testimony to Congress this spring, Homeland Security Secretary Michael Chertoff said that Operation Streamline "is a very good program, and we are working to get it expanded across other parts of the border" because "it has a great deterrent effect." The program is now in place in parts of Texas and Arizona.
But Melissa Wagoner, a spokeswoman for Sen. Edward M. Kennedy (D-Mass.), said there is a shortage of jail beds and public defenders in areas where the program is operating. "Operation Streamline in its current form already strains the capabilities of the law enforcement system past the breaking point," she said.
Others note that, historically, immigration violations have been processed by U.S. administrative courts. Criminalizing illegal immigration while turning a blind eye to employers who provide the jobs that lure migrants makes for good election-year politics but poor policy, said T.J. Bonner, president of the National Border Patrol Council.
"This strategy pretty much has it backwards," he said. "It's going after desperate people who are crossing the border in search of a better way of life, instead of going after employers who are hiring people who have no right to work in this country."
First piloted in December 2005 near Del Rio, Tex., Operation Streamline requires that virtually everyone caught illegally crossing segments of the border be charged with at least a misdemeanor immigration count and jailed until they are brought to court and, if convicted, eventually deported. A conviction jeopardizes any future legal entry to the United States.
Federal officials credit the program and other measures for contributing to a 20 percent drop in apprehensions of illegal immigrants on the U.S.-Mexico border in 2007, to 859,000. That figure is on track to drop an additional 15 percent this year.
While apprehension statistics can be misleading -- they obviously do not account for border-crossers who evade capture -- federal authorities say the decline coincides with a decrease in financial remittances from illegal immigrants in the United States to families in Mexico.
In areas where it has been applied -- which total about 500 miles, or one-fourth of the border -- Operation Streamline has slowed border traffic more substantially.
The number of apprehensions fell by nearly 70 percent in the last quarter of 2008 along a 120-mile stretch near Yuma, Ariz., after the program was phased in between December 2006 and June 2007, and by nearly 70 percent along the 210-mile span near Del Rio. Apprehensions fell 22 percent after Operation Streamline was initiated in October along 171 miles near Laredo, Tex.
Overall, the number of criminal immigration cases filed by U.S. prosecutors nearly doubled between January and February. They accounted for the majority of new Justice Department prosecutions nationwide in February -- about 7,250 out of 13,500 -- outnumbering all white-collar, civil rights, environmental and other criminal cases combined.
The surge in prosecutions accompanies other get-tough immigration-enforcement efforts, such as last month's raid on a kosher meatpacking plant in Iowa, where federal authorities detained 389 workers; 297 were convicted of immigration-related felonies, mainly using false documents to obtain jobs.
The prosecution data was collected by the Transactional Records Access Clearinghouse, an independent research organization at Syracuse University that analyzes monthly Justice Department prosecution statistics.
A Justice spokesman, Dean Boyd, challenged the specifics but not the conclusions of the group's findings, which are based on data compiled by the department's Executive Office for U.S. Attorneys. He said some of the increase in prosecutions may be due to improved reporting. The department declined last week to provide its own count of immigration prosecutions.
Attorney General Michael B. Mukasey said the program has had "great success" in areas with relatively low migrant traffic because the threat of imprisonment and criminal prosecution has sent a "major message" to most border-crossers, "who turn out to be people who are simply looking for work."
"It's worked beautifully. Crime has dropped 76 percent in Del Rio, with the lowest level of illegal crossings they have ever seen," said Rep. John Culberson, a Houston area Republican who has worked with two border-district Democrats to promote the program. "Law enforcement is simple if you just enforce the law rigorously."
But experts warn against exaggerating Operation Streamline's potential. The crackdown comes amid a softening U.S. economy, which tends to decrease illegal immigration. And migrants and smugglers have responded to past enforcement efforts by moving to more remote areas.
Mukasey said the program would be much more difficult to expand to high-traffic areas, such as the Tucson sector, where the Border Patrol made 378,000 apprehensions in 2007, nearly half its total. That number is more than three times the total apprehended in the Yuma, Laredo and Del Rio sectors combined.
In fact, Tucson is emerging as the battleground for Operation Streamline's "zero tolerance" concept, presenting a case study of the challenges in ramping up the nation's legal machinery to tackle the estimated 1 million-plus people a year who cross the border illegally or overstay their visas. Authorities there have launched a modified version of the program that they hope to expand in coming months.
John M. Roll, chief judge of the U.S. District Court of Arizona, said that since January, authorities from the Justice and Homeland Security departments and the federal courts have worked closely to increase Operation Streamline-related prosecutions. They began with 40 cases a day, are prosecuting 70 now and hope to reach 100 per day by September.
In four months this year, the court's magistrate judges imposed 3,700 sentences for Operation Streamline-related minor offenses, close to the 4,700 petty and misdemeanor cases they handled in all of 2007. The court also handled 2,800 felony cases, mostly immigration-related, in Tucson last year, for a total of about 7,500 cases, making it the nation's third-busiest.
Meeting the 100-case-a-day goal would nearly triple the court's workload, to more than 20,000 cases. But even that effort would address only about 5 percent of the apprehensions made in Tucson last year.
David Gonzales, the U.S. marshal for Arizona, said the program is swamping federal courthouses and jails.
"If [Streamline] was all we were doing, that would be fine. But we also have to deal with all other federal prisoners in southern Arizona and all other prisoners federal agencies bring in," Gonzales said.
Other federal officials are more critical, warning that the focus on immigration is distorting the functions of law enforcement and the courts. Several Arizona officials noted that U.S. prosecutors there last year were so short on resources, they chose not to prosecute a number of marijuana seizures of less than 500 pounds, although they later revised the guideline to 20 pounds.
"We're concerned about the misdirection of resources," said Heather Williams, first assistant to the federal public defender of Arizona. Each day her office's lawyers spend on misdemeanor border-crossing cases, she said, "they're not talking about a drug case, a sex crime, a murder, assault or any number of white-collar cases -- and the same is obviously true of the prosecutors."
"This is taking on a life of its own," she said.
Williams also warned that the program tests the U.S. legal system's promise of fairness to the accused. "If we as a U.S. citizen were placed in any other country on the planet, and had to resolve a case in a day that could result in being deported and having a criminal record, we would be outraged, and so would our government," she said.
Boyd, the Justice Department spokesman, said the government has not seen decreases in all other types of prosecutions and is increasing resources to support five border-area U.S. attorney's offices.
Michael Friel, a spokesman for U.S. Customs and Border Protection, the Homeland Security agency that includes the Border Patrol, said that even if Operation Streamline-related prosecutions near Tucson deter only a few illegal immigrants, that will free up resources that can be deployed elsewhere. He noted that U.S. authorities have been able to expand the program bit by bit since starting with a five-mile stretch near Del Rio.
"Obviously," Friel said, "we think it's proving to be an effective tool as part of a larger strategy to gain effective control of the border."