This week, the murder trial of Kate Steinle’s accused killer – Juan Francisco Lopez-Sanchez – is taking place in San Francisco. The senseless killing of this young woman in 2015 made national headlines when it was revealed that the perpetrator was an illegal alien who had been sheltered by San Francisco’s sanctuary policy.

Lopez-Sanchez, a citizen of Mexico, had been previously deported from the United States five times and had been released from San Francisco custody into the public rather than being turned over to ICE.

Such crimes are entirely preventable – if our immigration laws were fully enforced and the aliens weren’t in the country, then the crimes never would have happened. Confronted with such crimes committed by illegal aliens, the open-borders groups on the Left always respond the same way. They predictably trot out one of their favorite claims: the crime rate for aliens is less than it is for U.S. citizens.

However, there are two huge problems with this misleading claim: (1) it is based on flimsy data, and (2) it fails to differentiate between legal and illegal aliens.

The data problem has been explained in detail by demographic experts at the Center for Immigration Studies. The Left’s claim is based primarily on responses to surveys conducted by the Census Bureau and on analyses of prison populations. But when it comes to determining whether a prisoner is foreign-born or native-born, 53 percent of the time, the Census Bureau makes an educated guess. That’s a lot of guessing.

The second, and much bigger, problem with their claim is that they fail to differentiate between legal and illegal aliens. It would not be particularly surprising if it turned out that legal aliens residing in the United States commit crimes at a lower rate than U.S. citizens – because they are screened before they can obtain a visa. In other words, the criminals are excluded at the port of entry.

But illegal aliens are an entirely different matter. They are not screened before they enter, and the fact that they are willing to break our immigration laws suggests that they are more likely to break other laws too. There are many indicators in the crime data suggesting that illegal aliens commit crimes (other than their immigration crimes) at a much higher rate.

But don’t expect the open borders crowd to acknowledge that. They simply lump all “immigrants” together and declare them to be a low-crime population. U.S. citizens are a much more crime-prone lot, they tell us.

Of course, it is actually quite difficult to calculate exact crime rates for the illegal alien population, for several reasons. One is that we don’t the exact size of the total illegal alien population in the country. So you can get huge variations in the denominator, depending on which estimate you use.

Another reason is that there’s a lack of complete data concerning the imprisoned population. When the open-borders CATO Institute tried to estimate the crime rate for illegal aliens, they conceded that they couldn’t determine which alien prisoners in the survey were legally in the country and which ones were illegally present. So they made some laughably imprecise efforts to guess which prisoners were which, using “characteristics” they assumed might correlate will illegal status.

And finally, there’s the problem that many illegal alien criminals don’t ever make it into the prison system, because ICE takes them off of the prosecution track and puts them on the deportation track. It’s quite common for county prosecutors to drop a criminal prosecution of an illegal alien if ICE offers to remove him from the country. That means that the crime rate among illegal aliens is actually significantly higher than any estimates based on prison populations suggest.

Consequently, we will probably never be able to determine what the precise crime rate is for illegal aliens. But there is overwhelming evidence that it is much higher than the crime rate for U.S. citizens. Illegal aliens commit a disproportionate share of crimes:

Roughly 2/3 of these aliens were illegally in the country when they committed their crimes. So that’s over 14 percent of federal prisoners. Yet illegal aliens represent only 3-6 percent of the population. A grossly disproportionate share of federal prisoners – 22 percent – are aliens.Roughly 2/3 of these aliens were illegally in the country when they committed their crimes.So that’s over 14 percent of federal prisoners.Yet illegal aliens represent only 3-6 percent of the population.

75 percent of those on the most wanted criminals lists in Los Angeles, Phoenix and Albuquerque are illegal aliens.

More than 53 percent of burglaries investigated in the border region states of California, Nevada, Arizona, New Mexico, and Texas are committed by illegal aliens.

As of September 30, 2017, more than 232,000 aliens had been jailed, of which over 155,000 (2/3) were illegally in the country. The Texas Department of Public Safety has been keeping careful records of aliens booked into Texas jails since June 1, 2011.As of September 30, 2017, more than 232,000 aliens had been jailed, of which over 155,000 (2/3) were illegally in the country.

In FY 2015 (the last year for which we have complete statistics), And many more had been arrested or charged with crimes, but not yet convicted. Looking just at the aliens we are deporting, criminality is pervasive.In FY 2015 (the last year for which we have complete statistics), 59 percent of removed aliens had been convicted of criminal offenses (other than their immigration violations).And many more had been arrested or charged with crimes, but not yet convicted.

Every one of those crimes could have been prevented if the sanctuary policy had not been in place. ICE knows of nearly 10,000 additional crimes that were committed by illegal aliens who had been in the custody of sanctuary cities and counties, but were released.Every one of those crimes could have been prevented if the sanctuary policy had not been in place.

The bottom line is that illegal aliens present a disproportionate crime problem for this country. Kate Steinle is just one of thousands of Americans who have lost their lives as a result. To deny the connection between illegal immigration and crime is to deny reality. And to suggest that U.S. citizens commit crimes at an equal or greater rate is absurd.

Kris W. Kobach is the elected Secretary of State of Kansas. An expert in immigration law and policy, he coauthored the Arizona SB-1070 immigration law and represented in federal court the 10 ICE agents who sued to stop Obama’s 2012 executive amnesty. In 2017 President Trump named him Vice Chairman of the Presidential Commission on Election Integrity. His website is kriskobach.com.