There has been an elevated level of drug trafficking-related violence within and between the drug trafficking organizations (DTOs) in Mexico—a country with which the United States shares a nearly 2,000-mile border. Estimates have placed the number of drug trafficking-related deaths in Mexico between December 2006 (when then-Mexican President Felipe Calderón began his campaign against the DTOs) and December 2012 (when the Calderón administration ended) at somewhere between 45,000 and 55,000. While estimates of drug trafficking-related violence vary by the source, some have estimated the death toll for 2012 alone at over 9,575. This violence has generated concern among U.S. policy makers that the violence in Mexico might spill over into the United States. U.S. federal officials have denied that the increase in drug trafficking-related violence in Mexico has resulted in a spillover into the United States, but they acknowledge that the prospect is a serious concern. As an extension of its counternarcotics policy, as well as in response to the possibility of violence spillover, the U.S. government is supporting Mexico's crackdown campaign against DTOs in Mexico through bilateral security initiatives, including the Mérida Initiative. It is also enhancing border security programs and working to reduce the movement of contraband (drugs, money, and weapons) in both directions across the Southwest border. When discussing drug trafficking-related violence in the United States, one important point to note is that the mere presence of Mexican DTOs in the United States is not in and of itself an indication of any spillover of Mexican drug trafficking-related violence into the United States. While their presence may be an indication of the drug problem in general, it does not necessarily reflect activity directly tied to the recent violence seen in Mexico. The DTOs (Mexican and others) have been developing sophisticated illicit drug smuggling and trafficking networks for years. These activities engender violence and associated criminal activity, not just along the Southwest border but in other areas throughout the country, such as along domestic interstate distribution networks and in major metropolitan areas. The United States has experienced levels of drug trafficking-related crime for many years. The immediate question confronting policy makers is whether the elevated violence between DTOs in Mexico impacts either the level or character of drug trafficking-related violence in the United States. A related question is whether evidence of spillover violence would necessitate a policy response from Congress that is qualitatively different from the current efforts to combat drug trafficking. This report focuses on how policy makers would identify any spillover of drug trafficking-related violence into the United States. It provides (1) an overview of Mexican drug trafficking organization structures, how they conduct business, and the relationship between the drug trafficking organizations in Mexico and their partnerships operating here in the United States; (2) a discussion of the illicit drug trade between Mexico and the United States, as well as a discussion of factors implicated in drug trafficking-related violence; (3) an analysis of the possible nature of any spillover violence that may arise, as well as issues involved in accurately identifying and measuring such violence; and (4) an evaluation of available crime rate data and a discussion of how this data may or may not reflect changes in drug trafficking-related crime. This report does not include a discussion of illicit drug enforcement issues, nor does it include specific policy options that may be considered to stem a potential uptick in drug trafficking-related violence. The nature of the conflict between the DTOs in Mexico has manifested itself, in part, as a struggle for control of the smuggling routes into the United States. Therefore, the prospects for spillover violence are most keenly anticipated in the Southwest border (SWB) region of the United States because the region represents the arrival zone for the vast majority of illicit drugs that are smuggled into the country. The size, geography, and climate of the SWB region have long presented unique challenges to law enforcement. The southern border with Mexico stretches nearly 2,000 miles in length, is sparsely populated in some areas, and is dotted with legitimate crossing points (ports of entry)—both large and small. The National Drug Threat Assessment, 2008 , summarized the illicit drug threat scenario along the SWB in stark terms: The Southwest Border Region is the most significant national-level storage, transportation, and transshipment area for illicit drug shipments that are destined for drug markets throughout the United States. The region is the principal arrival zone for most drugs smuggled into the Unites States; more illicit drugs are seized along the Southwest Border than in any other arrival zone. Mexican DTOs have developed sophisticated and expansive drug transportation networks extending from the Southwest Border to all regions of the United States. They smuggle significant quantities of illicit drugs through and between ports of entry (POEs) along the Southwest Border and store them in communities throughout the region. Most of the region's principal metropolitan areas, including Dallas, El Paso, Houston, Los Angeles, Phoenix, San Antonio, and San Diego, are significant storage locations as well as regional and national distribution centers. Mexican DTOs and criminal groups transport drug shipments from these locations to destinations throughout the country. The most recent threat assessment indicates that the Mexican DTOs pose the greatest drug trafficking threat to the United States. Demand for illicit drugs in the United States partly drives this threat. The United States is the largest consumer of illegal drugs and sustains a multi-billion dollar market in illegal drugs. According to the Central Intelligence Agency, the United States is the largest consumer of Colombian-produced cocaine and heroin as well as Mexican-produced heroin and marijuana. It is also a large consumer of Mexican-produced methamphetamine. The latest National Household Survey on Drug Use and Health (NSDUH), in 2011, surveyed individuals aged 12 and older regarding their drug use during the previous month. In 2011, about 22.5 million individuals were current (in the past month) illegal drug users, representing 8.7% of individuals aged 12 and older. This percentage of users had remained relatively stable since 2002. Among these drug users, marijuana was the most commonly used drug, with an estimated 18.1 million users (7.0% of the population), followed by nonmedical use of prescription-type psychotherapeutic drugs (6.1 million users, or 2.4% of individuals). The survey also estimated that there were 1.4 million users of cocaine (0.5% of Americans), as well as nearly one million users of hallucinogens (0.4% of the population). Results also estimated 439,000 methamphetamine users (0.2% of the population). Mexican DTOs are the major suppliers and key producers of most illegal drugs smuggled into the United States across the SWB. Moreover, Mexico is the major transit country for cocaine. According to the U.S. State Department, "[a]pproximately 95 percent of the cocaine flow to the United States transits the Mexico-Central America corridor from its origins in South America." According to the National Drug Threat Assessment, 2011 , cocaine availability began decreasing in U.S. markets in 2007 and has remained below pre-2007 levels since then. The decreased cocaine availability has been attributed to a number of factors, including cocaine eradication, cocaine seizures, increased worldwide demand for cocaine, pressure on drug trafficking organizations in Mexico, inter-cartel violence, and border security. While cocaine availability decreased, the availability of heroin; marijuana; methamphetamine; and 3,4-Methylenedioxymethamphetamine (MDMA) remained, and even increased, in some areas. In addition to controlling most of the wholesale cocaine distribution in the United States, Mexican DTOs also control more of the wholesale distribution of heroin, methamphetamine, and marijuana than other major drug trafficking organizations in the United States. There has been an increase in heroin production in Mexico—including white powder, black tar, and brown powder heroin—and a subsequent increase in its availability in the United States. With respect to methamphetamine, there was a temporary decline in the supply of Mexican-produced methamphetamine beginning in 2006, in part because of Mexican import restrictions on precursor drugs beginning in 2006. However, by 2008, the DTOs had circumvented the Mexican chemical control laws and were using non-ephedrine based production methods, including the phenyl-2-propanone(P2P) method. This has enabled a subsequent uptick in Mexican methamphetamine flow into the United States. Marijuana availability in the United States has also increased due to factors such as rising marijuana production in Mexico, increasing marijuana cultivation in the United States led by criminal networks—including Mexican DTOs, and decreasing marijuana eradication in Mexico. The true quantity of drugs produced and transported by Mexican DTOs, however, is unknown. Available data provide insight into the quantity of drugs seized along the SWB, though this data cannot speak to the total amount of drugs produced and/or transported into the United States, nor does it provide information about the proportion of these drugs that are actually seized along the SWB. For instance, Table 1 illustrates federal seizures of illegal drugs along the SWB for calendar years (CY) 2005-2010. Total drug seizures (measured in kilograms) generally increased during this time period, despite declines in 2008 and 2010. The decline in seizures for 2010 was primarily driven by a nearly 141,000 kg drop in marijuana seizures compared to 2009. Additionally, cocaine seizures along the SWB decreased in 2007 and 2008 relative to previous years when cocaine seizures had been increasing, but seizures began to increase again in 2009, a year that was marked by an increase in all major illegal drug seizures except for seizures of MDMA. MDMA seizures continued to decline in 2010 as well. These data, however, do not provide insight into the total amount of drugs illegally produced and transported by the DTOs. Rather, these data reflect an unknown proportion of drugs that the Mexican DTOs are bringing into the United States through a variety of transportation modes. Mexican DTOs, in addition to being the major supplier of illegal drugs being smuggled into the United States, have a strong presence within the United States, operating in more than 1,200 U.S. cities. Mexican DTOs are transnational organized crime groups whose criminal activities center primarily around the drug trade. In general, organized crime groups attempt to fill particular illicit market niches. Specifically, DTOs respond to the societal demand for illegal drugs. Some experts have likened drug trafficking organizations to corporations or even small nation-states. They are influenced by factors such as geography, politics, economics, and culture. Geographically, for example, Mexican DTOs are situated between the world's largest producer of cocaine (Colombia) and the world's largest consumer of cocaine (United States), leading Mexico to be a natural drug transshipment route between the two countries. In addition, major Mexican criminal organizations focus primarily (though not exclusively) on drugs, because the drug trade has, to date, generally proven to be more economically lucrative than other illicit activities such as kidnapping and extortion. Nonetheless, Mexican DTOs have diversified their operations, adding to their portfolio crimes ranging from kidnapping and extortion to human trafficking and intellectual property rights violations. These enterprises may help the DTOs supplement their drug trafficking-related income. Mexican DTOs either (1) transport or (2) produce and transport drugs north across the United States-Mexico border. Figure 1 illustrates the drug trafficking routes within Mexico and at the United States-Mexico border. After being smuggled across the border by DTOs, the drugs are distributed and sold within the United States. The illicit proceeds may then be laundered or smuggled south across the border. The proceeds may also be used to purchase weapons in the United States that are then smuggled into Mexico. This leads to a general pattern of drugs flowing north across the border and money and guns flowing south. Although Mexican DTOs have been active for some time, they have become more prominent since the decline of the powerful Colombian DTOs beginning in the 1980s. The National Drug Intelligence Center (NDIC), in its 2009 threat assessment, estimated that Mexican DTOs maintain drug distribution networks—or supply drugs to distributors in at least 230 U.S. cities, as illustrated in Figure 2 . More recent NDIC estimates reportedly indicate that the DTOs have expanded operations and are present in at least 1,286 U.S. cities. Of these operations, 143 are reported to be controlled directly by DTO members in Mexico. Mexican DTOs annually transport multi-ton quantities of illicit drugs from Mexico into the United States using a variety of multi-modal transportation methods. Estimates are that these drugs generate between $18 billion and $39 billion in U.S. wholesale drug proceeds for the Colombian and Mexican DTOs annually. When conceptualizing Mexican drug trafficking organizations as businesses, policy makers may question the impact of possible drug trafficking-related violence spillover (into the United States) on the drug trafficking business —selling drugs in the U.S. black market. Although the effects of violence on businesses in the black market may not mirror those effects on business in the licit market, one way of examining this question may be to look at the impact that violence or violent crimes have on business in general. One study, for example, examined the impact of surges in violence on businesses in various industries in locations of varying crime rates. Results suggested that surges in violence had the most negative impact on those businesses that were service-related (e.g., retail and personal service industries) and located in typically low-crime areas. Specifically, the impact on business was in terms of a reduction in the number of new businesses, a decrease in business expansions, and a lack of overall business growth. In order to generalize these findings from retail businesses to drug businesses, one underlying assumption must be that the locations for buying retail goods and personal services are the same as those for purchasing drugs. If these findings can be generalized to the drug trafficking business, this could suggest that any spillover in drug trafficking-related violence to the United States could adversely affect those service-related businesses (including drug trafficking businesses) in cities with relatively (pre-spillover) low crime rates. On the other hand, if violence affects businesses in the licit and illicit markets differently, these findings may not apply to potential effects of drug trafficking-related violence on drug trafficking business. There have been anecdotal predictions regarding the impact of violence on drug trafficking business; Douglas, AZ, police chief Alberto Melis has said that "spillover violence would be bad for business ... and they're [the drug traffickers] businessmen." Further, the Drug Enforcement Administration (DEA) has expressed moderate confidence that there will not be a significant increase in spillover violence—at least in the short term—because "Mexican trafficking organizations understand that intentional targeting of U.S. persons or interests unrelated to the drug trade would likely undermine their own business interests." Some have suggested that major acts of violence in the United States would lead to a federal law enforcement response. And, the resulting incarceration of perpetrators would be detrimental to the drug trafficking business. The NDIC has indicated that in order to facilitate the distribution and sale of drugs in the United States, Mexican DTOs have formed relationships with U.S. street gangs, prison gangs, and outlaw motorcycle gangs. Although these gangs have historically been involved with retail-level drug distribution, their ties to the Mexican DTOs have allowed them to become increasingly involved at the wholesale level as well. These gangs facilitate the movement of illicit drugs to urban, suburban, and rural areas of the United States. Not only do these domestic gangs distribute and sell the drugs, but they also "provide warehousing, security, and/or transportation services as well." For example, Barrio Azteca is one of at least nine prominent U.S. prison gangs with ties to Mexican DTOs. Barrio Azteca primarily generates money from smuggling marijuana, heroin, and cocaine across the Southwest border for the DTOs—namely, the Juárez cartel—but they are also involved in other crimes, such as extortion, kidnapping, and alien smuggling. Like other organized crime groups, Mexican DTOs are profit-driven. While the primary goods trafficked by DTOs are drugs, some experts have noted that these organizations do generate income from other illegal activities, such as the smuggling of humans and weapons, counterfeiting and piracy, kidnapping for ransom, and extortion. If the DTOs are not able to generate income from the drugs—due to any number of reasons (increased Mexican or U.S. law enforcement, decreased drug supply, decreased drug demand, etc.)—they may increase their involvement in other money-generating illegal activities, such as kidnapping and home invasions. Take, for example, the number of drug trafficking-related kidnappings for ransom in Phoenix, AZ. In 2009, the NDIC reported 358 such incidents in 2007 and 357 in 2008 (through December 15, 2008), and indicated that nearly every incident was drug-related. These statistics were revised in the 2010 National Drug Threat Assessment, indicating that kidnappings in Phoenix reached 260 in 2007, 299 in 2008, and 267 in 2009. This decrease in the number of reported kidnappings for 2007 and 2008 was reportedly due to a reclassification of certain cases by the Phoenix Police Department. Further, the NDIC reports that kidnappings may be generally underreported because victims may fear retaliation for reporting or may expose their own involvement in drug trafficking. Still, Tucson, AZ, police have reported that although there has been an increase in kidnappings for ransom and home invasions, the suspects in the cases are local criminals—not active DTO members from Mexico. This disparity in reports indicates that while there may be an increase in certain illegal activities that may be tied to drug smuggling and trafficking, these illegal activities are not necessarily directly related to drug trafficking in general or to Mexican drug trafficking organizations in particular. As such, they may not be valid or reliable indicators for the presence or absence of drug trafficking-related spillover violence. In an illegal marketplace, where prices and profits are elevated due to the risks of operating outside the law, violence or the threat of violence becomes the primary means for settling disputes and maintaining a semblance of order—however chaotic that "order" might appear to the outside observer. This was a fundamental conclusion reached by the National Academy of Sciences Panel on the Understanding and Control of Violent Behavior. Because illegal drug markets operate outside the law, no courts or other forms of peaceful mediation exist for resolving disputes between drug producers, traffickers, and their customers. As with other black markets, drug markets are necessarily governed by the threat of violence, which may lead to actual violence. Illegal drugs and violence, then, are linked primarily through the operations of underground drug markets. Drug trafficking-related violence in Mexico has been elevated, particularly since 2007, and in 2012, there were over 9,575 drug trafficking-related murders in Mexico. Mexican drug trafficking organizations are now at war with each other as well as with the police and military personnel who are attempting to enforce the drug laws in northern Mexico along the U.S. border. The DTOs, as a result of enforcement actions in Mexico, along with increasing border enforcement measures taken by the United States, are finding it more difficult and more costly to control the production zones and smuggling routes. One of the consequences of this increasingly competitive environment is a rise in the level of violence associated with the illicit drug trade as the DTOs struggle for control over territory, markets, and smuggling routes. Policy makers are thus confronted with the uncomfortable possibility that increased law enforcement (which leads to increased difficulty and costs to control production zones and smuggling routes, and which in turn leads to the need to resolve disputes over such territories) could result in increased drug trafficking-related violence. This appears to be the situation that has developed in Mexico. This relationship gives rise to a number of important issues for policy makers. One such matter is evaluating the relative costs and benefits of increased enforcement of the current drug policy against the potentially elevated levels of violence that such increased enforcement might engender. Could the drug trafficking-related violence currently evidenced in Mexico reach a level that would prompt U.S. policy makers to consider policy actions that could alter the underpinnings of the illegal drug market? It does not appear as if the violence has reached such a level as yet. Policy makers, however, have expressed significant concern over the possibility of the current violence in Mexico spilling over into the United States. When assessing the potential implications of increased violence in Mexico as a result of the increasing tensions between the DTOs located in Mexico, one of the central concerns for U.S. policy makers is the potential for what has recently been termed "spillover" violence—an increase in drug trafficking-related violence in United States. Given this concern, it is critical to develop an understanding of what "spillover" is, what it might look like, how it might be measured, and what potential triggers for policy action can be identified from this analysis. To date, Congress has not adopted a formal definition of spillover violence. Several definitions and/or qualities of spillover violence have been provided by government officials, as well as experts and analysts. For instance, according to the DEA, the interagency community has defined spillover violence in the following manner: [S]pillover violence entails deliberate, planned attacks by the cartels on U.S. assets, including civilian, military, or law enforcement officials, innocent U.S. citizens, or physical institutions such as government buildings, consulates, or businesses. This definition does not include trafficker on trafficker violence, whether perpetrated in Mexico or the U.S. This definition of spillover provides a relatively narrow scope of what may constitute spillover violence. In particular, it excludes the category of violence—trafficker-on-trafficker violence—in which the vast majority of drug trafficking-related violence in Mexico has occurred. If policy makers and law enforcement are concerned that the drug trafficking-related violence, as seen in Mexico, may spill over into the United States, they are necessarily concerned with this predominant category of trafficker-on-trafficker violence that is excluded from the interagency community's definition of spillover violence. The boundaries of what may constitute spillover violence, as defined by the interagency community, thus makes the likelihood that the United States will experience this form of spillover violence relatively small. Further, by generally constraining the definition of spillover violence to those acts that target the government and innocent civilians, the type of violence necessary to constitute spillover (according to the interagency definition) may begin to resemble acts of terrorism. If so, policy makers and experts may be challenged with discriminating between spillover violence and terrorism. Several experts and scholars have also discussed qualities of drug trafficking-related violence that may constitute spillover, including aspects of trafficker-on-trafficker violence. Such qualities are analyzed in the following section and may provide policy makers with additional definitions of spillover violence. Of note, this report does not address non-violent indicators—such as rising corruption of U.S. officials and law enforcement—that could be related to drug trafficking-related violence spillover. Some experts have suggested that a spillover of violence into the United States may look similar to the recent surge of violence in Mexico. In Mexico, this increasing violence has been seen through a rise in both the number of drug trafficking-related murders and the brutality of the murders. It is also taking the forms of increasing intimidation and fear, attacks on security forces, assassinations of high-ranking officials, growing arsenals of weapons, and indiscriminate killing of civilians. While a potential spillover of violence into the United States could appear similar to the violence in Mexico, the violence may be contingent upon numerous factors that differ between the United States and Mexico. For instance, the U.S. government may respond differently to domestic drug trafficking-related violence than the Mexican government has, and these differences in responses could in turn influence the nature of the drug trafficking-related violence seen in each country. This section of the report discusses several factors that may be of concern as Congress debates the potential spillover of drug trafficking-related violence. These factors include who may be implicated in the violence, what type of violence may arise, when violence may appear, and where violence may occur. If the drug trafficking-related violence were to spill over from Mexico into the United States, Congress may be concerned with both the individuals perpetrating the violence as well as the victims of the violence. Reports on the drug trafficking-related violence in Mexico generally indicate that the perpetrators of violence are active members of DTOs who are vying for territory, avenging betrayals, and reacting against the Mexican government's crackdown on the traffickers. If violence were to spill into the United States, policy makers may question whether the perpetrators of the violence will continue to be active drug trafficking members from Mexico, or whether violence will be inflicted by others who may be more indirectly tied to the DTOs. As mentioned, the DTOs have connections with U.S. groups such as street gangs, prison gangs, and outlaw motorcycle gangs who distribute and sell drugs, aid in smuggling drugs, and enforce the collection of drug proceeds. To date, reports from law enforcement on drug trafficking-related violence in the United States are mixed; while some suggest that violence may be carried out by drug traffickers or other criminals from Mexico, others indicate that domestic drug traffickers or gang members may be responsible. The violence plaguing Mexico has been directed toward several groups: competing DTOs vying for territory, Mexican security forces, government officials, and those indebted to the traffickers. In fact, Mexican government officials have estimated that 90% of the murders in Mexico have targeted members of drug trafficking organizations. Although there have been reports of civilian bystanders being killed and isolated events of indiscriminate killing, there are not consistent reports of the drug traffickers targeting civilians who are unconnected to the drug trade. There have been concerns, however, raised by the isolated incidents of U.S. law enforcement agents killed both in the United States and in Mexico by suspected drug smugglers and traffickers. For example, U.S. Border Patrol Agent Brian Terry was killed in December 2010 in Arizona, and in February 2011, two ICE agents were shot, one fatally, while driving between Monterrey and Mexico City. Experts have suggested that "[i]f the current security trends [in Mexico] continue to worsen ... the deliberate and sustained targeting of U.S. government personnel will become more likely." If there were to be a significant spillover of violence into the United States, policy makers may question whether the victims would be of a similar group as the victims of violence in Mexico. To date, the anecdotal reports of drug trafficking-related violence in the United States indicate that not only the perpetrators, but the victims of the crimes as well, are all somehow involved in the drug trade. If any significant spillover of drug trafficking-related crime were to follow a similar pattern, policy makers could expect that individuals on both sides of the violence are connected to the drug trade. There are circumstances, however, under which the drug trafficking victims in the United States could extend to groups beyond those involved in trafficking. If there is an increase in violence and the U.S. government cracks down on the DTOs similarly to the Mexican government, the traffickers' reactions in the United States may be similar to that seen in Mexico—a surge in violence against security forces and government officials. Of note, overall violence against federal law enforcement officials along the SWB has remained relatively constant over the past several years, with 1,056 assaults against border patrol agents in FY2009 and 1,049 in FY2010. Examining specific sectors, however, has revealed localized changes—increased assaults against border patrol agents in the Tucson, AZ, and El Paso, TX, sectors coupled with decreased assaults against agents in the San Diego, CA, sector. It is unclear what proportion of these assaults—if any—may have been carried out by members or affiliates of Mexican DTOs. Federal officials have indicated that increased targeting of U.S. law enforcement personnel, similar to that which has occurred in Mexico, would constitute evidence of spillover. If, however, the U.S. response differs from that of Mexico, the reactions from the DTOs may also differ. Further, a change in the victim pattern—to include innocent bystanders, for instance—may represent a departure from current patterns of drug trafficking-related violence and thus could represent a reasonable trigger for policy action to mitigate the effects of spillover violence. In Mexico, the drug trafficking-related violence most often reported is murder. Estimates are that there were somewhere between 45,000 and 55,000 drug trafficking-related murders between December 2006 and the end of 2012. There have also been reports of kidnappings, home invasions, and assaults, among other crimes. In the United States, many of the anecdotal reports citing an increase in violence point to an increase in drug trafficking-related kidnappings and home invasions. However, the true number of these crimes across the country, and how many have clear ties to drug trafficking, is unknown. It is also unknown whether or not different types of violence are more associated with certain crimes (committed by drug traffickers) than with others. If there were to be a substantial spillover of drug trafficking-related violence from Mexico, policy makers and law enforcement may be concerned with what types of violence may appear. Would the types of drug trafficking-related violence already seen in the United States to date (i.e., kidnappings and home invasions) become more prevalent, or would there be a greater emergence of the types of violence seen in Mexico (i.e., murders)? In addition to the type of violence, a spillover or increase in violence could also be measured by the nature of the violence. As mentioned, the rise in the number of murders in Mexico was also accompanied by increasing brutality, intimidation, and attacks on individuals other than those directly involved in the illicit drug trade (i.e., security forces and governmental officials). If any spillover of violence into the United States followed a similar pattern as the violence in Mexico, there may be an increase in the brutality of crimes in addition to an increase in the pure number of crimes. Critical to the assessment of whether the United States is experiencing spillover violence is the establishment of a realistic timeline for measuring the change in drug trafficking-related violence in the United States. If the policy goal is to determine if any spillover violence is occurring in the United States as a result of the increasing violence in Mexico, then it would be logical to look at trends in drug trafficking-related crime in the United States since the onset of the conditions that precipitated the recent violence in Mexico—roughly beginning around when former Mexican President Felipe Calderón took office in December, 2006. A comparison of the trends in drug-trafficking related violence (in the United States) before and after this reference point might shed some light on whether or not the United States is experiencing spillover violence. As noted, the United States has experienced and continues to experience certain levels of drug trafficking-related crime. It may be difficult to isolate those drug trafficking-related violent crimes that are occurring either directly or indirectly as a result of the situation in Mexico. Therefore, it may also be useful for policy makers to use this same timeframe to measure changes in other spillover indicators, such as changes in the profile of victims of drug trafficking-related crime, the number and nature of violent attacks on U.S. law enforcement personnel, and changes in the nature of drug trafficking-related violence. This could be one means to standardize the measurement of any potential spillover and to provide policy makers with a more concrete idea of the trends. The discussion of when the violence occurs begs the question of where to measure any potential change in violence. As may be expected, the majority of the discussion surrounding the prospects of spillover violence in the United States has been focused on the Southwest border (SWB). Initially, this makes intuitive sense. Even the very term "spillover" suggests the spread of violence across the border from Mexico—almost by osmosis. From a policy perspective, it is useful to question whether or not a focus exclusively on the border makes sense. Certainly this is where the analysis should begin as the SWB region is the primary region that links production and smuggling operations within Mexico to the United States. As noted, however, the drug trafficking organizations' operations within the United States are geographically dispersed in as many as 1,286 or more cities. DTOs are businesses, and they not only maintain their own presence in the United States but also have relationships with U.S. groups such as street gangs, prison gangs, and outlaw motorcycle gangs to facilitate the distribution and sale of drugs within the United States. Given that drug trafficking-related violence is prevalent throughout the United States, the task for policy makers is to concentrate the geographic analysis of changes in drug trafficking-related violence around areas that would have the greatest likelihood of eliciting evidence of spillover. One possible method of accomplishing this task could be to look at the various factors discussed above—changes in the levels, nature, and victim pattern of drug trafficking-related violence in selected geographic locations—along a timeline that corresponds with the escalation of drug trafficking violence in Mexico. Of course, the critical issue is selecting those geographic locations. Areas already identified as strategically important to drug trafficking operations here in the United States would be an optimal place to start. These locations would include cities, states, and localities in the SWB region, as well as along significant inland distribution routes. Policy makers may also wish to examine geographic areas that are not currently identified as strategically important to drug trafficking operations here in the United States, as a control for comparison. This section of the report discusses some of the challenges facing policy makers when considering policy options dealing with drug control and border security issues in general. These issues are discussed more generally because they provide the context within which any specific options for dealing with the potential spillover of drug trafficking-related violence will be determined. These policy challenges include the complexity of the issue, defining goals and objectives, and measuring the problem. As evidenced through some of the above discussion, there are many federal agencies, state and local entities, task forces, intelligence centers, and various other groups that are not only involved in drug control policy in general, but have specific roles in countering threats posed by the Mexican DTOs. Each of these agencies has different authorities, budgets, resources, and responsibilities when it comes to the drug control issue. This complexity has also been evident in the federal government's current response to the increasing drug trafficking-related violence in Mexico. The policy implication of this intricate web of jurisdictions is that it is difficult to centralize the establishment, implementation, and evaluation of policies—be they drug control policies in general, or the specific policy responses to the increased drug trafficking-related violence in Mexico. Several congressional hearings have been held on various aspects of the drug control and drug trafficking-related violence issues, and some congressional policy makers have voiced their concerns over the lack of centralized direction on these issues. In particular, some in Congress have expressed concern over who is taking the lead—not just among the involved agencies—but within Congress itself. Complicated congressional jurisdiction spread across a variety of committees in both houses means that oversight of the drug control and the drug trafficking-related violence issues is equally complex. Consequently, coordination of oversight of the areas is problematic and difficult to manage. Adding further complexity is the fact that few of the agencies involved in the drug control effort are solely dedicated to a counterdrug mission (DEA and ONDCP being two of few exceptions). This presents several challenges in analyzing drug control policy. One challenge, for example, involves disaggregating an agency's drug control mission and activities from its other missions and activities. Take, for instance, interdiction at ports of entry. CBP officers select people, goods, and conveyances for additional scrutiny based on a variety of factors. Often, officers have no idea what the ultimate outcome of a physical inspection might be. The inspection might uncover illicit drugs, or it might uncover cash, weapons, or any number of items that are prohibited from entering the country. How then, may one estimate the portion of CBP officers' time that is spent on the counterdrug effort? This same question applies to the multitude of other agencies that also have drug control responsibilities. The question becomes even more difficult to answer when the aim is to analyze a specific drug control policy—such as specific policies targeted toward any potential spillover violence from Mexico. Disaggregating the drug control mission (or specific policies), however, is critical on several levels; not only does it affect the measurement of an agency's progress in implementing drug control efforts, but it also affects the directing of resources towards these efforts or specific policies. The definition of success is a critical aspect of policy evaluation. As noted above, the existing complexities surrounding drug control policies in general, and policies to address the potential spillover violence from Mexico in particular, complicate the evaluation of these policies. For this reason, it is important to identify appropriate goals or objectives either for what might be an overall strategy or for specific policies. For example, the appropriate domestic policy response to the increased drug trafficking-related violence in Mexico is difficult to articulate. This is because several forces are at work; it is tempting to conflate the response to a specific iteration of the problem (the change in drug trafficking-related violence in Mexico) with the drug control problem in general and, at the same time, to disaggregate the issue down to so many constituent parts (outbound inspections at the border, kidnappings in Phoenix, straw purchases in Houston, a drug trafficking-related shooting in El Paso, etc.). This allows for the potential to obscure the actual policy problem to be confronted. From a policy perspective also, the degree to which this conflation or disaggregation occurs may not matter in the final analysis if the appropriate metrics are ultimately used to evaluate each. With particular relevance to the subject of this report, if the policy task is to identify any potential or actual drug trafficking-related spillover violence in the United States, and the appropriate drug activity indicators can be accurately identified, the issue becomes how to correlate any change in drug activity indicators to the increased drug trafficking-related violence in Mexico. One potential complication with such an analysis is uniformly defining what constitutes drug-related violence. This could potentially be broken down into three general categories: crimes committed by people under the influence of drugs; economic-compulsive crimes (crimes committed in order to obtain money or drugs to support drug use); and what are termed systemic drug crimes—crimes that result from the business of trafficking illicit drugs. These definitions are important, because while the commission of crimes by people who are under the influence of illegal drugs and economic-compulsive crimes present important policy issues in and of themselves, changes in these indicators contribute little value to the determination of whether or not the United States is experiencing any spillover violence from Mexico particularly related to the elevated level of drug trafficking-related violence . The issue of measurement is important in several different contexts. There are issues with the collection and reporting of drug control statistics, as well as questions concerning what value the reported measures have. Because the drug control issue is complex, and so many agencies participate in its execution, invariably there are going to be differences in how agencies collect and report enforcement statistics. Central to the issue at hand in this report is the question of how to measure changes in drug-related violence, and specifically drug trafficking-related violence. Even an indicator that conceptually could provide some value added to the central question (to choose an example popularly cited in the media—violent crimes excluding robberies) is difficult to evaluate. For example, in Tucson, the number of violent crimes excluding robberies from January to March of 2009 was 632; for the same period in 2008 the number was 651. So, there were fewer violent crimes in Tucson in the first three months of 2009 than in 2008. These are not necessarily drug trafficking-related violent crimes, but if the premise—that the United States is experiencing spillover violence stemming from the drug trafficking activity in Mexico—is accurate, one would expect violent crimes to go up, and drug trafficking-related violent crimes would be included in the more general violent crime reporting. On the other hand, a significant drop in non-drug trafficking-related violence could obscure a rise in actual drug trafficking-related violent crime. However, the true driver of the change in drug trafficking-related violent crime cannot be ascertained from these statistics. Another measurement issue is where to look for changes in drug-trafficking-related violence. This is another area where the problems with available data are manifested. Ideally, to conduct this analysis, one would have access to drug-trafficking-related violent crime data from the geographic areas of interest (border and interior locations with known drug trafficking activity). This data would be available in small geographic increments so that local differences could be taken into account, and it would be consistently available in comparable sets across an adequately long time period so as to conduct a statistically significant trend analysis. Unfortunately, this and other data are not readily available for analysis, as detailed in the section outlining the Congressional Research Service's (CRS's) evaluation of available data. As discussed, a multitude of factors are involved in both defining as well as measuring spillover violence. Currently, there is no comprehensive, publicly available data that can definitively answer the question of whether there has been a significant spillover of drug trafficking-related violence into the United States. Although anecdotal reports have been mixed, U.S. government officials maintain that there has not yet been a significant spillover. In an examination of data that could provide insight into whether there has been a significant spillover in drug trafficking-related violence from Mexico into the United States, CRS undertook an analysis of violent crime data from the FBI's Uniform Crime Report (UCR) program. Of note, however, the UCR data does not allow analysts to determine what proportion of the violent crime rate is related to drug trafficking or, even more specifically, what proportion of drug trafficking-related violent crimes can be attributed to spillover violence. The UCR compiles data from monthly reports from approximately 17,000 local police departments or state agencies, and it provides some of the most commonly cited crime statistics in the United States. Under the UCR program, the FBI collects data on the number of offenses known to police, the number and characteristics of persons arrested, and the number of "clearances" for eight different offenses, collectively referred to as Part I offenses. Part I offenses include murder and nonnegligent manslaughter, forcible rape, robbery, aggravated assault, burglary, larceny-theft, motor vehicle theft, and arson. Within the Part I offenses, crimes are categorized as either violent or property crimes. Violent crimes include murder and nonnegligent manslaughter, forcible rape, robbery, and aggravated assault. Property crimes include burglary, larceny-theft, motor vehicle theft, and arson. The UCR, however, is not a comprehensive source for data on crime in the United States. It collects offense data on a limited number of crimes (Part I crimes), which means that offense data are available only for a small number of all crimes committed in the United States. For instance, it does not include data on kidnapping—one of the oft-cited drug trafficking-related crimes discussed as evidence of spillover violence. Further, the inclusivity of the UCR data is affected by other factors such as whether or not local law enforcement chooses to report data to the FBI, the variety in reporting and data classification practices of local law enforcement agencies, and the imputation methods used by the FBI to estimate crime in jurisdictions that have not reported for an entire year. For the purpose of this report, CRS presents and analyzes violent crime rates as reported by the UCR program, as policy makers have repeatedly expressed concern about the possibility of drug trafficking-related violent crimes increasing. In addition to providing the overall national violent and property crime rates annually, the UCR program also provides these crime rates for metropolitan statistical areas (MSAs). In the present analysis of violent crime rate data, CRS relies upon the violent crime rate data for the MSAs as calculated by the UCR program. As mentioned, the violent crime rate includes murder and nonnegligent manslaughter, forcible rape, robbery, and aggravated assault. As mentioned, the NDIC estimated in its 2009 threat assessment that Mexican DTOs maintain drug distribution networks—or supply drugs to distributors in at least 230 U.S. cities (as illustrated in Figure 2 ). It was later noted that DTOs have expanded operations and are present in at least 1,286 U.S. cities. Because this information is assimilated based on state and local law enforcement agency estimations, as well as law enforcement interviews with NDIC staff, this is not necessarily a comprehensive or nuanced picture of Mexican drug trafficking presence in cities around the United States. For instance, while some cities may experience a larger amount of drug trafficking activity than others, these cities are considered as equally experiencing drug trafficking presence for the purpose of the NDIC estimate. In addition, there may be other cities not reporting the presence of DTOs, even if these organizations are active in those cities. If drug trafficking-related violence is in fact increasing in those cities reporting a presence of Mexican DTOs, one may expect to see an increase in such violence in the cities identified by the NDIC—or perhaps only in those cities that are situated along the SWB if the violence is truly spilling directly across the border. Further, if this increase in violence were to follow a similar time frame as the escalating violence in Mexico, one may expect to see an increase in violence since December 2006, when former Mexican President Felipe Calderón took office and began to crack down on the DTOs. For each of the 230 cities cited by the NDIC's 2009 threat assessment as having Mexican DTO presence, CRS determined whether there was a corresponding MSA and violent crime rate reported in the UCR for that MSA. CRS identified 138 such MSAs, 8 of which directly abut the border between the United States and Mexico. CRS refers to these 8 as the "border MSAs" and the other 130 MSAs that do not directly abut the U.S.-Mexico border as the "non-border MSAs." As illustrated in Figure 3 , CRS calculated the average violent crime rate across the border MSAs and the non-border MSAs for each of the years 1999 through 2011. CRS analysis of available data suggests that the violent crime rate has not significantly increased in those areas where there is an identified presence of Mexican DTOs, as well as available data on the violent crime rate for those MSAs. Further, such analysis suggests there is no statistically significant difference in the average violent crime rate in these border and non-border MSAs between the years 1999 and 2011. Since 2001, the average violent crime rate in the eight selected border MSAs has generally declined, and it has remained below the national violent crime rate since 2005. It is unknown, however, whether trends in the violent crime rate are related to changes in drug trafficking-related violent crimes. Because the violent crime rate is a compilation of violent crimes both related and unrelated to drug trafficking, an increase in drug trafficking-related violent crime could be masked by a decrease in those violent crimes not related to trafficking—or vice versa. Looking at the aggregate of border and non-border MSAs, however, may not provide information as to trends in individual MSAs or cities. For example, Figure 4 illustrates the trends in violent crime rates in eight border MSAs. As mentioned, if spillover violence were to trend in time with the escalating violence in Mexico, analysts may expect to see an increase in drug trafficking-related violence between 2007 and 2011 relative to previous years. For instance, although one MSA—El Paso, TX—experienced an increase in the violent crime rate in 2007, 2008, 2009, and 2010 compared to 2006, the violent crime rate in the El Paso MSA remained lower than the violent crime rate in that MSA from 1999-2004. Further, when drug trafficking-related violence peaked in Mexico in 2011, the violent crime rate in El Paso dropped, as did the violent crime rate in six of the seven other border MSAs depicted in Figure 4 . These trends may be counterintuitive to some who expect that a "spillover" in violence may touch those cities closest in proximity to the violence in Mexico. Spillover violence may not occur uniformly across the entire SWB during the same time periods. There may be hot-spot "flare-ups" in response to Mexican drug trafficking activity directly across the border. If this were true, violence would have climbed in Laredo, TX, in 2004 and 2005 when there was an increase in drug trafficking-related violence across the border in Nuevo Laredo. It did not. Also using this hot-spot analysis, the more recent increase in violence in Ciudad Juarez should be linked to an increase in violence in El Paso, TX, between 2008 and 2010. In this case, an increase in violence in a Mexican city does appear to be correlated with an increase in violence in a neighboring U.S. city. This further illustrates that relying on trends in overall violent crime rates may not provide an accurate depiction of trends in violent crime (or more specifically, in drug trafficking-related violent crime) around the country. Another possibility is that there may be a time lag between drug trafficking-related violence in Mexico and any associated violence in the United States. For instance, after settling territorial disputes in Mexico, rival DTOs may engage in violent conflict on the U.S. side of the border. With the data available, however, it is not possible to separate out a time lag from other factors that may influence levels of drug trafficking-related violence that may be seen in the United States. Mexico has experienced an elevated level of drug trafficking-related violence within and between the drug trafficking organizations (DTOs), and the number of drug trafficking-related deaths in Mexico between December 2006 (when then-Mexican President Felipe Calderón began his campaign against the DTOs) and December 2012 (when the Calderón administration ended) has been estimated at somewhere between 45,000 and 55,000. Congress remains concerned with the possibility that the current drug trafficking-related violence in Mexico may spill over into the Untied States. One of the primary challenges in assessing this violence is defining the term spillover . While the interagency community has defined spillover violence as violence targeted primarily at civilians and government entities—excluding trafficker-on trafficker-violence—other experts and scholars have recognized trafficker-on-trafficker violence as central to spillover. When defining and analyzing changes in drug trafficking-related violence within the United States to determine whether there has been (or may be in the future) any spillover violence, critical elements include who may be implicated in the violence (both perpetrators and victims), what type of violence may arise, when violence may appear, and where violence may occur (both along the Southwest border and in the nation's interior). At present, there is no comprehensive, publicly available data that can definitively answer the question of whether there has been a significant spillover of drug trafficking-related violence into the United States. Although anecdotal reports have been mixed, U.S. government officials maintain that there has not yet been a significant spillover. CRS analyzed violent crime data from the Federal Bureau of Investigation's (FBI's) Uniform Crime Report program in order to examine data that could provide insight into whether there has been a significant spillover in drug trafficking-related violence from Mexico into the United States. However, the overall violent crime data do not allow CRS to determine the proportion of violent crimes that are related to drug trafficking or, even more specifically, the proportion of drug trafficking-related violent crimes that are attributable to spillover violence. In its analysis, CRS calculated the average violent crime rate across eight selected Metropolitan Statistical Areas (MSAs) along the Southwest border and 130 selected non-border MSAs—identified by the National Drug Intelligence Center (NDIC) as having the presence of Mexican DTOs—for each of the years 1999 through 2011. CRS analysis suggests that the violent crime rate has not significantly increased in those areas where there is an identified presence of Mexican DTOs. Further, there appears to be no significant difference in the average violent crime rate in the selected border and non-border MSAs between the years 1999 and 2011. In conclusion, however, because the trends in the overall violent crime rate may not be indicative of trends in drug trafficking-related violent crimes, CRS is unable to develop fact-based conclusions about trends in drug trafficking-related violence spilling over from Mexico into the United States.

Summary: There has been an elevated level of drug trafficking-related violence within and between the drug trafficking organizations in Mexico. This violence has generated concern among U.S. policy makers that the violence in Mexico might spill over into the United States. U.S. federal officials have denied that the increase in drug trafficking-related violence in Mexico has resulted in a spillover into the United States, but they acknowledge that the prospect is a serious concern. The most recent threat assessment indicates that the Mexican drug trafficking organizations pose the greatest drug trafficking threat to the United States, and this threat is driven partly by U.S. demand for drugs. Mexican drug trafficking organizations are the major suppliers and key producers of most illegal drugs smuggled into the United States across the Southwest border (SWB). The nature of the conflict between the Mexican drug trafficking organizations in Mexico has manifested itself, in part, as a struggle for control of these smuggling routes into the United States. Further, in an illegal marketplace—such as that of illicit drugs—where prices and profits are elevated due to the risks of operating outside the law, violence or the threat of violence becomes the primary means for settling disputes. When assessing the potential implications of the increased violence in Mexico, one of the central concerns for Congress is the potential for what has been termed "spillover" violence—an increase in drug trafficking-related violence in United States. While the interagency community has defined spillover violence as violence targeted primarily at civilians and government entities—excluding trafficker-on-trafficker violence—other experts and scholars have recognized trafficker-on-trafficker violence as central to spillover. When defining and analyzing changes in drug trafficking-related violence within the United States to determine whether there has been (or may be in the future) any spillover violence, critical elements include who may be implicated in the violence (both perpetrators and victims), what type of violence may arise, when violence may appear, and where violence may occur (both along the SWB and in the nation's interior). Currently, no comprehensive, publicly available data exist that can definitively answer the question of whether there has been a significant spillover of drug trafficking-related violence into the United States. Although anecdotal reports have been mixed, U.S. government officials maintain that there has not yet been a significant spillover. In an examination of data that could provide insight into whether there has been a significant spillover in drug trafficking-related violence from Mexico into the United States, CRS analyzed violent crime data from the Federal Bureau of Investigation's Uniform Crime Report program. The data, however, do not allow analysts to determine what proportion of the violent crime rate is related to drug trafficking or, even more specifically, what proportion of drug trafficking-related violent crimes can be attributed to spillover violence. In conclusion, because the trends in the overall violent crime rate may not be indicative of trends in drug trafficking-related violent crimes, CRS is unable to develop fact-based conclusions about trends in drug trafficking-related violence spilling over from Mexico into the United States.