Those who support amnesty and nonenforcement of our immigration laws don’t like to talk about how much illegal immigration costs American citizens. But a March report from the Government Accountability Office (GAO) graphically illustrates some of those costs, which go far beyond dollars.

GAO found that one of every four inmates in federal prisons is an illegal immigrant. And that number is rising. Since 2005, the number of criminal aliens in federal prison has increased by 7 percent.

Two thirds (68 percent) of those incarcerated aliens came from Mexico. Just think of how much less crime we would have if we put in the manpower and resources required to stop the flow of illegal immigrants across our Southern border.

Of course, not all illegal immigrants convicted of criminal activity are housed in federal prisons. Washington provides partial reimbursement (about 23 percent) to states that incarcerate criminal aliens through the Justice Department’s State Criminal Alien Assistance Program (SCAAP). GAO estimates nearly 300,000 SCAAP aliens are confined in state and local prisons — a 35 percent increase from 2003.

Two-thirds (66 percent) of SCAAP prisoners are locked up in just six states — California, Texas, Arizona, Florida, New York and Illinois. California alone holds more than 100,000 — at huge cost to state taxpayers — while Texas incarcerates 37,000. As with federal inmates, the vast majority (66 percent) of aliens in state prisons are from Mexico.

Obviously, these incarcerated aliens represent a huge drain on taxpayers. The criminal justice system — from investigation to arrest to prosecution and imprisonment — does not come cheap. But the cost in terms of the safety and lives of American citizens is even higher — indeed, incalculable. GAO found “criminal aliens were arrested about 1.7 million times, averaging about 7 arrests per criminal alien.” Their offense records were even worse: “A total of 2.9 million offenses, averaging about 12 offenses per criminal alien.”

And what were those offenses? GAO’s random sample of 1,000 criminal aliens found that half were arrested at least once for assault, homicide, robbery, a sex offense (such as rape) or kidnapping. About 50 percent were arrested at least once on drug charges. In New York, the primary offense for which aliens were convicted in 2008 was homicide. From 2005 through 2008, drugs, sex crimes and assault were the top three offenses for illegal immigrants imprisoned by states seeking reimbursement under the SCAAP program.

But many of these aliens had multiple arrests in their record (which raises the question of why they were in a position to commit a second offense):

• More than a quarter (28 percent) had six to 10 arrests.
• Another 11 percent had 11 to 15 arrests.
• 3 percent had rap sheets revealing 21 or more arrests.

Had those criminals been detained and deported when first arrested, hundreds of thousands of Americans would not have been victimized by their subsequent crimes.

It is quite true that some illegal immigrants re-enter the country after they have been deported and then commit more crimes. But the fact that they are able to re-enter so easily goes back to the initial problem we have: that not enough is being done to secure our borders.

So we get victims such as the 16-year-old girl in Miami who, after attending church, was raped recently by an illegal immigrant from Guatemala, a crime that might not have happened but for our nonenforcement policies. The tally of victims also includes thousands of people no longer with us — the GAO report lists more than 25,000 homicide arrests of aliens — as well as their grieving families and friends.

What we need is an administration that:

• Encourages states to help enforce our immigration laws (The current administration is suing states that try to help.)
• Sues cities with sanctuary policies that violate federal law.
• Uses all of the federal resources at its disposal to find, detain and deport illegal immigrants.
• Is willing to prosecute employers who knowingly hire illegal immigrants.
• Implements all of the measures needed to finally secure our border.

Only then will Americans stop being victims of needless — and preventable — crimes committed by illegal immigrants. Only then will taxpayers stop getting hit with the costs of tracking down and incarcerating (and feeding, providing medical care for, etc.) people who violate the law to get here. As the GAO study suggests, a large number of those who break the law to enter our country keep on breaking it once they arrive.

Hans A. von Spakovsky is a senior legal fellow at the Heritage Foundation.