EDINBURG -- The Rio Grande Valley will be the next place to implement a zero-tolerance policy credited with slashing illegal immigration rates by almost 70 percent in other parts of the state.

Dubbed "Operation Streamline," the plan calls for the criminal prosecution of every migrant caught crossing the border without proper documentation, U.S. Border Patrol officials said Tuesday.

And while the program has had dramatic results in largely rural parts of Texas and Arizona, it remains untested in more populous regions where the number of immigrants apprehended each year is typically higher.

Skeptics fear prosecution of every illegal immigrant could overwhelm local federal courts, which already spend much of their time on immigration-related cases.

"We will prioritize our resources to ensure those who enter illegally are removed expeditiously," U.S. Attorney Don DeGabrielle said in a statement. "Operation Streamline recognizes the critical importance of detention and immediate removal as a deterrence to future illegal immigration."

STATISTICAL SUCCESS

The Border Patrol rolled out the policy Monday along a four-mile stretch of Cameron County's border with Mexico from Brownsville to Fort Brown, local Border Patrol spokesman Ricardo Rosas said.

All undocumented immigrants arrested there now will be detained, sent to court, jailed for up to 180 days if found guilty and then deported.

Formerly, first-time offenders were offered the option of voluntary deportation and were processed, put on a bus and sent back to Mexico within hours of their arrest.

Rosas would not say whether plans had been drafted to expand Streamline for the entire Rio Grande Valley Border Patrol Sector, which runs from Brownsville to Rio Grande City.

But in Del Rio, where agents implemented the Streamline policy in December 2005, immigration arrests have dropped by 67 percent over the last two years.

Officials saw similar results in Yuma, Ariz., and Laredo, where apprehensions have dropped by 70 percent and 22 percent, respectively, since Streamline's start in those areas.

The U.S. Department of Homeland Security often points to declining immigration apprehensions as a sign that fewer people are attempting to cross the border illegally. Although the statistic does not address those who successfully manage to enter the country unnoticed, it does coincide with an overall decrease in monetary remittances sent back to Mexico in recent years.

"The word has gotten out through Mexico and Central America," Del Rio-based Border Patrol Supervisory Agent Hilario Leal told The Monitor in November. "People know not to cross in Del Rio and to try and cross somewhere else."

COURT OVERLOAD?

Unlike Del Rio, however, which reported 18,286 apprehensions last year, agents in the Rio Grande Valley Sector arrested 73,430.

Federal courts in the region already handle twice as many immigration cases as the next highest ranked district, according to a report released last year by the Administrative Office of the U.S. Courts.

And there are signs that the targeted prosecutions have already strained smaller districts.

"We don't have as much time as we'd like to handle each case," said Del Rio-based Federal Public Defender William Fry, whose office is often appointed by judges to handle the cases of illegal immigrants caught up in Streamline.

"We'll get a case on Wednesday and the court expects us to be back and ready to go by Friday. That's not enough time to adequately represent a client."

But Border Patrol spokesman Rosas said Tuesday that it was too early to tell what kind of effect Streamline would have in the Valley.

"This operation is really to deter illegal crossers," he said. "We'll have to see what happens."

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Jeremy Roebuck covers courts and general assignments for The Monitor. You can reach him at (956) 683-4437.