The US immigration crisis is the result of a violence crisis in Central America. But the violence has not reached all parts of Central America, and thus the migrants are primarily coming from Honduras, El Salvador, and Guatemala. In these countries, a LAPOP study (using UN data) shows murder rates much higher than in the rest of the region and in Honduras that rate has reached almost 10 times that of Panama, Costa Rica, and most surprisingly, Nicaragua. What explains the Nicaraguan exception?
The explanation for Nicaragua's exceptionalism is not related to the economy, or its ability to spend more resources on police patrols. Further, unlike Costa Rica and Panama, it has poor relations with the United States, so foreign aid in fighting gangs or narco-traffickers is not an option.
The first potential explanation was underscored in a 2012 Economist article. Their explanation focuses on Aminta Granera, Nicaragua's popular police chief, whom they describe as a former "nun and guerrilla." (She is also a graduate of Thomas More College, a Catholic liberal arts college in the United States.) They also note that the police "are aided by 100,000 volunteers. These include law and psychology students; 10,000 former gang members, who mentor youths via baseball in the barrios; and nearly 4,000 domestic-violence victims, who persuade women to speak out."
Political scientists, public policy experts, and other academics are often uncomfortable with explanations that rely on the extraordinary contributions of a single person. We are thus interested in the policies or structures that explain the much lower level of violence in Nicaragua. Ms. Granera's 2014 report to the president (as reported in a news article ) highlights successes in terms of attacking distribution "webs" and many arrests. As in the Economist article, she also gives credit to the 300,000 people working to keep drugs out of Nicaragua, including 30,000 student volunteers who are organized into the "Popular Breastplate (Coraza) Plan," which reduces costs by 35% and has "kept 4 million doses of crack from reaching the youth." She notes, too, the support of the army. Finally, she also gives credit to the social and economic programs targeted at the poor.
The community policing is also a focus of an InSight Crime article. Discounting the importance of arms seizures, the analysts for this think tank focusing on crime again cite the role of Nicaragua’s volunteer police system with keeping narco-traffickers at bay.
There are many models of community policing, both within and among countries. In a comparative study, with most contributors from the MSU School of Criminal Justice, researchers describe one model in Mexico that was based on trained but unarmed retired teachers and doctors. Another Mexican community ran an almost-autonomous police force, given their frustration with the state services. This community even set up a community judicial system, in which suspects are judged and sentenced through a "community assembly." In the United States, the term often has a much more narrow definition, simply implying that officers patrol on foot. It can, however include what one MSU study called "auxiliary-reserve-volunteers," neighborhood response units, and horse patrols.
Most of these studies do not provide solid empirical evidence to support views that these models reduce crime. The editors of the book on community policing state that there is little such evidence, partially due to the difficulty in defining success. They state, however, that most authors find the attempts "laudable and desirable." A 1994 CRS report, however, was less sanguine, citing a study done in Houston that found no impact of the program. 
In a study that specifically focuses on crime rate differences across Central America, Florida International University political scientist Jose Miguel Cruz, explains that the post-war reforms in Nicaragua transformed "security institutions into rule-of-law institutions." He also argues that the revolution removed "violent entrepreneurs acting on behalf of the state" in Nicaragua, thus helping to limit the penetration by corrupt and crime-oriented actors. This positive outcome, he argues, was the result of the Sandinistas destroying the Somoza dictatorship but then losing the election in 1990. Then, with pressure from the United States, the new president (Chamorro) eliminated most Sandinistas from the security institutions. Sandinistas did retain an important role in the military, but it was institutionalized and the police gained autonomy from the armed forces.
In a conversation, Cruz added that the Nicaraguans have been successful at addressing crime, without always resorting to force as in other Central American countries. Instead, they intervene with families and try to deal with issues before they become serious problems. Further, they have implemented these programs in spite of poverty and very poorly paid police. If these programs do deserve the credit for the low crime rates, then investments in early intervention, community policing, and social programs have provided tremendous returns.
In sum, while there is not a consensus on explanations, and little solid evidence in support of the theories, several studies point to better policing as a source of Nicaragua's lower levels of violence. Still, the drug gangs are not ignoring Nicaragua. In 2012 a judge was arrested for using his post to smuggle drugs, raising concerns that the narco-traffickers had indeed penetrated the Sandinista government. Last week brought a different type of warning, as a politically-motivated attack left five dead and 28 injured in attacks on two buses. Perhaps the arrest of the magistrate, as well as several people involved in the bus attack, shows the effectiveness of the Nicaraguan police system. It also shows, however, the pressure that it faces.
 http://www.economist.com/node/21543492 “A Surprising Safe Haven.” Jan 28th 2012.
 El 19: Martes 8 de Abril 2014 Primera Comisionada Aminta Granera presenta Informe Anual 2013 de la Policía Nacional; http://www.el19digital.com/articulos/ver/titulo:17634-primera-comisionad....
 Roy Fenoff and Karina Garcia, "Mexico," in Nalla, Mahesh K. and Graeme R. Newman eds. 2013. "Community Policing in Indigenous Communities" CRC Press .
 "The Status of Contemporary Community Policing" Robert C. Trojanowicz and Hazel A. Harden 1985. National Neighborhood Foot Patrol Center. http://cj.msu.edu/assets/Outreach-NCCP-GB3.pdf
 David Teasley, 1994. "Community Policing: An Overview Congressional." Research Service.
 José Miguel Cruz. “Criminal Violence and Democratization in Central America: The Survival of the Violent State." Latin American Politics and Society, 2011. 53-4.