Illegal immigration and crime became a hot topic this election cycle as soon as Donald Trump burst into the Republican primary with his call to build a wall to keep criminal illegal aliens out of the country. Such policy discussions have fallen by the wayside as the election cycle morphed into a mudslinging fight of personal insults and accusations of sexual assaults, but the link between illegal immigration and crime is still worth discussing, especially since Trump's initial highlighting of the issue fueled his rise.

Here are nine things you need to know about illegal immigration and crime.

1. Federal, state and local governments keep data involving illegal immigration and crime out of the public purview. Fox News reported in 2015 that a source from Immigration and Customs Enforcement (ICE) said "that comprehensive statistics on illegal immigrant crime are not available from the federal government, and suggested contacting county, state and federal jail and prison systems individually to compose a tally, a process that would encompass thousands of local departments."

Former Department of Justice attorney J. Christian Adams also told Fox News that some states do readily track illegal immigration and crime, but they withhold the specific numbers from the public out of fear of backlash from the federal government or for political purposes.

However, there is still some data that can be pieced together to examine illegal immigration and crime, and evidence suggests that there is a correlation between the two.

2. Available evidence suggests that illegals are more likely to commit crimes than the rest of the population. Fox News sorted through myriad "local, state and federal statistics" and found that "illegal immigrants are three times as likely to be convicted of murder as members of the general population and account for far more crimes than their 3.5-percent share of the U.S. population would suggest."

The percentage of illegals committing the number of crimes are as follows, according to Fox News:

  • 13.6 percent of those sentenced for all committed crimes in the country
  • 12 percent of murder sentences
  • 16 percent of trafficking sentences

3. Almost 50 percent of federal crimes were committed near the Mexico border. A report from the Department of Justice in 2014 found the following, via Judicial Watch:

Of the 61,529 criminal cases initiated by federal prosecutors last fiscal year, more than 40%—or 24,746—were filed in court districts neighboring the Mexican border. This includes Arizona, New Mexico, Southern California, Western Texas and Southern Texas. The two Texas districts each had more than double the convictions of all four federal court districts in the state of New York combined, according to the DOJ report. The Western Texas District had the nation’s heaviest crime flow, with 6,341 cases filed by the feds. In Southern Texas 6,130 cases were filed, 4,848 in Southern California, 3,889 in New Mexico and 3,538 in Arizona.

Not surprisingly, most of the offenses were immigration related. In fact, 38.6% of all federal cases (23,744) filed last year involved immigration, the DOJ report confirms. Nearly 22% (13,383) were drug related, 19.7% (12,123) were violent crimes and 10.2% (6,300) involved white-collar offenses that include a full range of frauds committed by business and government professionals. This is hardly earth-shattering news in fact, the nation’s southern border region has for years been known for its high crime rate compared to the rest of the country.

Judicial Watch also notes that the crimes near the border had been spiking at such an "alarming rate" that "Mexican and American journalists have largely stopped reporting it," whether for ideological reasons or to avoid backlash from the drug cartels.

4. Illegal immigrants accounted for nearly 75 percent of federal drug sentences in 2014. This is according to the United States Sentencing Commission, which also found that illegals were involved in nearly 17 percent of drug-trafficking sentences and over 33 percent of federal sentences overall.

5. A disproportionate amount of illegals are in state prisons. Peter Kirsanow, a member of the U.S. Commission on Civil Rights and a lawyer, reviewed statistics from the Government Accountability Office and Pew Research Center and compared the number of illegals and non-illegals imprisoned for murder-related offenses in a 2015 National Review piece. Some of his findings:

  • There were 68.57 illegal aliens imprisoned for every 100,000 illegals in Arizona, compared to 54.06 citizens and legal noncitizens imprisoned for every 100,000 citizens and legal noncitizens.
  • There were 97.2 illegals imprisoned for every 100,000 illegals in California, compared to 74.1 citizens and legal noncitizens imprisoned per 100,000 citizen and legal noncitizens.
  • There were 54.85 illegals imprisoned for every 100,00 illegals in Florida, compared to 67.8 legal immigrants imprisoned for every 100,000 legal immigrants.
  • There were 168.75 illegals imprisoned for every 100,000 illegals in New York, compared to 48.12 legal immigrants imprisoned for every 100,000 legal immigrants.
  • There were 54.54 illegals imprisoned for every 100,000 illegals in Texas, compared to 65.43 legal immigrants .

Kirsanow acknowledged that while comparing murder incarceration rates isn't a perfect measurement, "it’s difficult to contend that illegal aliens are more law-abiding than legal residents — at least when it comes to major crimes." But the more disturbing fact was that "approximately 2,430 illegal aliens are in prison just for homicide-related offenses" in California alone.

"If one assumes that each illegal alien so imprisoned was responsible for just one homicide-related offense, that amounts to about a couple thousand major crimes that, arguably, wouldn’t have occurred but for the actors’ unlawful presence in the United States," Kirsanow notes. "That translates to thousands of American citizens (and others) across the country slaughtered by individuals who shouldn’t have been here in the first place."

6. Tens of thousands of criminal illegals have been released by ICE and are at large in the country. In 2015, ICE released almost 20,000 illegals that committed 64,000 crimes that involve "12,307 drunken driving convictions, 1,728 cases of assault, 216 kidnappings and more than 200 homicide or manslaughter convictions," according to the Washington Times. It's even worse when one considers the fact that the Obama administration released "86,000 illegal immigrants who have committed over 231,000 crimes in just the past two and a half years," according to Independent Journal Review.

7. The rise in illegals crossing the border has fueled gang violence. In March, the Daily Caller reported that the barbaric MS-13 gang has been recruiting young illegals, resulting in higher crime in the Washington, D.C area. In fact, Montgomery County in Maryland "has seen an unprecedented level of gang-related violence in the last 8 months - with illegal immigrant youth being responsible for 85 percent of street robberies," according to IJ Review. The horrors of MS-13 have extended to the Brentwood community in Long Island, NY, where the remains of a dead teenager was found for the fifth time in six weeks, likely the result of MS-13.

8. Sanctuary cities have hampered law enforcement in cracking down on gangs. Heather Mac Donald documented the frustrations of Los Angeles law enforcement officers in 2004 when they couldn't touch known gang members because of their status as illegals:

“We can’t even talk about it,” says a frustrated LAPD captain. “People are afraid of a backlash from Hispanics.” Another LAPD commander in a predominantly Hispanic, gang-infested district sighs: “I would get a firestorm of criticism if I talked about [enforcing the immigration law against illegals].”

The issue is that these gang members tended to sneak back into the country even after they were deported for heinous crimes, and police officers couldn't enforce immigration laws against them and would have to resort to surveilling these gang members until they commit a crime.

While these statistics from Mac Donald's piece are dated, it illustrates just how badly the sanctuary policy has hampered crime:

• In Los Angeles, 95 percent of all outstanding warrants for homicide (which total 1,200 to 1,500) target illegal aliens. Up to two-thirds of all fugitive felony warrants (17,000) are for illegal aliens.

• A confidential California Department of Justice study reported in 1995 that 60 percent of the 20,000-strong 18th Street Gang in southern California is illegal; police officers say the proportion is actually much greater. The bloody gang collaborates with the Mexican Mafia, the dominant force in California prisons, on complex drug-distribution schemes, extortion, and drive-by assassinations, and commits an assault or robbery every day in L.A. County. The gang has grown dramatically over the last two decades by recruiting recently arrived youngsters, most of them illegal, from Central America and Mexico.

• The leadership of the Columbia Lil’ Cycos gang, which uses murder and racketeering to control the drug market around L.A.’s MacArthur Park, was about 60 percent illegal in 2002, says former assistant U.S. attorney Luis Li. Francisco Martinez, a Mexican Mafia member and an illegal alien, controlled the gang from prison, while serving time for felonious reentry following deportation.

Unsurprisingly, violent crime has skyrocketed recently in Los Angeles as illegal immigration has surged. In fact, crime among sanctuary cities in general has increased.

9. Crime has also increased among major cities that are "immigration hubs." Daily Wire editor-in-chief Ben Shapiro has written:

David Frum of The Atlantic, no hard-core immigration opponent, wrote in 2015 that as of 2011, there were 25,000 illegal immigrants serving murder sentences, and nearly 3 million offenses committed by illegal immigrants between 2003 and 2009, including 70,000 sex crimes and hundreds of thousands of other violent crimes. “After years of welcome decline,” Frum pointed out, “crime rates are rising in immigration hubs including Houston, Milwaukee, Phoenix, and San Diego.” Former Colorado Congressman Tom Tancredo reported in 2015 that between “2008 and 2014, 40% of all murder convictions in Florida were criminal aliens. In New York it was 34% and Arizona 17.8%. During those years, criminal aliens accounted for 38% of all murder convictions in the five states of California, Texas, Arizona, Florida and New York, while illegal aliens constitute only 5.6% of the total population in those states.

Some individual examples of those who were victimized by illegals can be seen here and here.

Top image (Getty Images): A U.S. Border Patrol agent leads of group of captured undocumented immigrants near the U.S.-Mexico border late on August 19, 2016 near Hidalgo, Texas.