An accused illegal immigrant murderer’s apparent success in beating an employment background check exposes the “Achilles’ heel” of the E-Verify system, according to immigration experts.

Law enforcement authorities this week charged Cristhian Bahena Rivera with murdering college student Mollie Tibbetts in Iowa. Rivera’s employer, Yarrabee Farms, confirmed Tuesday that the defendant worked at the farm.

Co-owner Dane Lang initially told reporters that the farm had used the instant E-Verify check to confirm his legal status. But Lang later corrected the record and said the farm had not used E-Verify.

Lang told reporters that Rivera (pictured center above) supplied a state-issued photo identification and Social Security card. A senior law enforcement officer told The New York Times that the identification that Rivera used had been stolen.

Experts said even if Rivera had used E-Verity, he may have beaten it if he had a Social Security number and identification belonging to an actual person.

“This kind of identify theft is the Achilles’ heel of E-Verify,” said Jessica Vaughan, director of policy studies at the low-immigration advocacy group Center for Immigration Studies (CIS).

The E-Verify system searches government databases and either confirms a new hire is authorized to work, rejects him, or flags him as potentially ineligible, giving the worker several days to resolve the discrepancy.

Vaughan said E-Verify flags would-be workers if they submit documentation that is phony. But she said illegal immigrants who purchase the “total package” from identify theft rings — often for a few hundred dollars — can get a Social Security number and matching driver’s license of a real person.

“People can get by E-Verify if they’re in the country illegally … This has been a known issue with E-Verify,” said Chris Chmielenski, director of content and activism at NumbersUSA.

To critics of E-Verify, the Rivera case is a prime argument for scrapping it. Alex Nowrasteh, an immigration policy analyst at the libertarian Cato Institute, told The Mercury News in San Jose that E-Verify is “full of holes and it doesn’t work” — just like Swiss cheese.

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“E-verify looks at the paperwork that people give to their employer,” he said. “It approves the documents — it doesn’t approve the worker. That’s a big loophole.”

Matthew O’Brien, director of research at the Federation for American Immigration Reform (FAIR), agreed — up to a point,

“E-Verify is a database,” he said. “It’s only as good as the information in it.”

But O’Brien rejected the argument that E-Verify should be cast aside because it is not foolproof.

“It’s still worth doing,” he said. “It gives employers a way of weeding out 95 percent of the fraud.”

Chmielenski said Congress could make fraud much harder. He pointed to Legal Workforce Act, a bill sponsored last year by Rep. Lamar Smith (R-Texas), that would phase in mandatory use of E-Verify by businesses and take steps to prevent identity theft. The bill would allow any citizen to lock his Social Security number to prevent it from being used by another person to get a job.

It would require that a Social Security holder be notified if his number has been used for multiple jobs. Chmielenski said the Social Security Administration, by policy, does not alert people when this happens now.

Vaughan said the loophole is easy enough to close.

“This is not rocket science,” she said. “If the same Social Security number is used in different places, there are computer systems that can find that.”

Vaughan said she suspects the government is reluctant because it fears the “sheer numbers (of compromised Social Security numbers) that will show up.” She said the Department of Treasury has estimated that as many as 8 million Social Security numbers my be compromised, although not all are related to illegal laborers.

“I think we really only know the tip of the iceberg of how much identify theft happens in this country,” she said.

O’Brien said Congress could require companies to examine physical documents and not just run information through a computer system. It also could add more databases to the system to make it harder to defeat through fraud, he added.

Related: Mollie Tibbetts’ Alleged Murderer Worked Less Than Three Miles from Where She Was Staying

“There’s a number of things we can do about these things if we’re really interested in doing it,” he said.

Chmielenski said the E-Verify system itself is simple to use. He said his organization has used it for new hires since the system debuted in the mid-1990s. An employer enters information that federal government already requires on an I-9 form and then runs it through the database.

“We’ll get notified within seconds of hitting the button,” he said.