But this distinct jump in prosecutions for the nation as a whole was entirely the result of an even more unusual increase in the federal criminal referrals from Customs and Border Protection (CBP) agents. A total of 1,881 more CBP-referred criminal prosecutions occurred in December, a surge of nearly one-third from the previous month's count. See Table 1.

With the possible reform of immigration laws a top priority issue for the Obama Administration, Congress and a wide range of public interest groups, changes in how current laws are being enforced could have significant political implications for all parties.

This sharp increase in CBP-referred prosecutions was not felt along the whole southwest border with Mexico. Instead, it was almost entirely focused on just two of the border's five federal districts: Texas South and Texas West. In fact, in each of these districts there was a 50 percent or higher jump in prosecutions, largely for illegal entry. (The growth was mainly concentrated in their Laredo and Del Rio offices.)

The enforcement trends in these two hot spots contrasted sharply with the patterns that were found in three other border districts — Arizona, New Mexico and California South. Both Arizona and New Mexico showed declines of 25 percent or more. The Southern District of California (San Diego) also fell, but by a lower amount (7 percent). See tables at the end of this report for the figures by federal district (Table 3) and office within each southwest border district (Table 4).

The reasons for the major jump in prosecutions in Texas South and Texas West — but not in other border districts — are unclear. One possible explanation is that there has been a surge in the apprehensions in these locales. (The government has not yet published these counts.) A second possibility is that the agents working in the two districts have adopted a tougher enforcement policy. The CBP public affairs office in Washington has failed to respond to two separate queries by TRAC to determine which, if either, explanation is correct.

Another unusual aspect of the recent surge is that it did not follow the usual seasonal pattern of recent years in which December counts have been historically low relative to other months, presumably reflecting fewer apprehensions at that time of year. (The cyclical changes for the last four years are shown in Figure 1.) The pronounced rise in prosecutions in November and December thus marks a striking departure, with the December count the highest seen in any month of the Obama Administration.

Figure 1. CBP-Referred Criminal Prosecutions, December 2008 - December 2012

Analysis of tracking databases maintained by the office of each U.S. Attorney uncovered both the overall prosecution counts for the nation as a whole and the dramatic, hard-to-explain changes in the enforcement actions in two of the nation's 90-plus federal districts. These databases are released to TRAC on a monthly basis by the Executive Office for United States Attorneys as a result of Freedom of Information Act (FOIA) litigation brought by TRAC.

Illegal Entry Prosecutions Dominate

Included in the case-by-case records obtained by TRAC is information about what the Justice Department calls the "lead charge" and the sentence that was imposed. The data show that the majority of defendants received no prison time other than time served while waiting for their cases to be resolved (see Table 2). During the first three months of FY 2013, nearly three out of four prosecutions (73 percent) were for illegal entry, a petty offense under Title 8 Section 1325 of the United States Code. In second place were prosecutions for illegal re-entry, a more serious felony charge. A total of 20 percent were re-entry prosecutions. For those convicted on the basis of the second charge the median prison sentence was 6 months.

Looking across the list of lead charges, almost all prosecutions (96 percent) were for some type of immigration violation. Prosecutions involving drugs made up only 3.5 percent.

What Do the Increases in Border Prosecutions Signify?

As noted above, a jump in criminal prosecutions could reflect either an increase in border apprehensions in Texas or a harsher policy for sanctioning individuals who have been caught. The Bush-initiated Operation Streamline, which began in December 2005, announced "zero tolerance" for illegal entry across specific segments of the U.S.-Mexico border, and called for federal criminal charges to be brought for every person who crossed the border illegally. This continues to be the official policy under President Obama.

(A criminal prosecution, of course, is not the only sanction that can be imposed on individuals who have been apprehended while illegally crossing the border. Customs and Border Protection agents also possess the authority to remove individuals administratively without the need for any order by a judge. This so-called "expedited removal" bars individuals from re-entering the United States again from some years. But Operation Streamline shifted the focus to criminal prosecution.)

Operation Streamline, plus the expanding number of border patrol agents, resulted in a deluge of criminal prosecutions for illegal entry and illegal re-entry that flooded federal courts situated along the southwest border with Mexico. See TRAC report documenting the early impact of Operation Streamline.

However, the number of Border Patrol apprehensions was generally declining at the point that Operation Streamline went into effect. It was inevitable that at some point the declining number of apprehensions along the border caught up with the expanding proportion of these apprehensions being criminally prosecuted. As a result, Border Patrol referrals for criminal prosecution began falling. As TRAC recently reported, a CBP spokesman in November 2012 explained this decline in CBP-referred prosecutions as a direct result of the fall in border apprehensions:

"We believe that the investment the American people have made in personnel, infrastructure and technology on the borders of the United States are continuing to pay dividends in the form of lower apprehension numbers."

(There are, of course, other influential factors, including shifts in the U.S and Mexican economies. For more numbers on these trends see TRAC's June 2012 report.)

Thus, the unusually high December 2012 prosecution figures are noteworthy not only because they are so high but because these numbers appear to mark a clear reversal in trends. While comparable data for January and February of 2013 are not yet available, a federal public defender spokesperson for the Del Rio, Texas area indicated that numbers of defendants they are currently seeing during February has remained significantly high compared with previous months.

So what has caused this jump? TRAC contacted parties involved in processing criminal cases or in border security; those who were willing to speak stated that they knew of no change in policy or in staffing that might explain the increase. Federal prosecutors prosecute virtually all referrals they receive from Customs and Border Protection, so the real issue is: does the jump in CBP referrals to federal prosecutors reflect a real increase in apprehensions along the South and West Texas border?

As noted above, as of this time the CBP's public affairs office in Washington has not responded to two queries from TRAC. The Border Patrol press officers for both hot spots — Laredo, Texas and Del Rio, Texas — were also contacted. The Del Rio spokesperson, Dennis Smith, indicated that the rise reflected in CBP referrals recorded by the U.S. Attorney's office in December "should" reflect rising border patrol apprehensions. However, he was unwilling to release the actual Border Patrol apprehension numbers that would corroborate whether this was true. The BP spokesperson for the Laredo office didn't return our phone calls.

An alternative explanation for the jump would be that there has been increased emphasis on tough border enforcement accompanying the Administration's push to pass immigration reform, but why this would mostly happen in only two districts is unclear.