Think of the four-digit PIN number for your automatic-teller card.

Now, think of it with the four digits in reverse order.

Now imagine doing that with a gun held to your back.

The sobering question of whether that’s something an average ATM customer could do under the stress of a robbery is at the core of a distinctly modern debate about bank-customer safety — a debate focused not on alarms and locks, but on software and psychology.

It’s a debate that also has raised what should be a simple statistical question: Just how likely are you to get robbed at one of the nation’s roughly 400,000 ATMs? Not even the banking industry can say — a data lapse that Joseph Zingher believes is intentional.

Zingher, a lawyer and inventor, has patented a system that he says would give people a way to safely alert police when they’re being robbed and ordered to make ATM withdrawals. The system would allow the user to enter the regular PIN number backward, which would dispense the money and look to the robber like a normal transaction — but would alert police, silently, to the robbery in progress.

Cases it could help

The point isn’t to stop the theft, Zingher says, but to ensure that the police are on their way, giving them that much of an earlier start in the pursuit if the robber abducts the customer. Such a system, he argued, could save lives.

Specifically, Zingher mentioned a high-profile case in Wichita, in which two brothers abducted five people from a townhouse in December of 2000, terrorized them for several hours and forced them to withdraw money from ATMs before shooting all five in the head. Only one victim survived.

Eight days before the murders, one of the brothers had abducted another victim and forced him to withdraw money from an ATM before releasing him unharmed.

In theory, Zingher’s system also could have shortened the ordeal of a woman from Chesterfield, Mo., who was abducted from her apartment last month, forced at knifepoint to drive in her own car to withdraw money from her ATM account, then released several hours later.

“If they’re taking you to your ATM to get money … that ATM may be your only chance to call for help,” said Zingher, 47, who lives in the Chicago suburb of Beach Park, Ill. “This could protect human life, and it would be cheap to do.”

In addition to alerting police to the robbery, Zingher said, the system would give police all the information the bank has about the victim — which could include the victim’s home address, car license number, and perhaps even a facial image — helping police in the search.

Zingher first proposed the “reverse-PIN system” idea more than 10 years ago, and since then has been granted the patent on it and received the endorsement of various police groups for its use. But it’s still not being used anywhere in the country.

Industry rejects plan

The banking industry has rejected the very concept of it and has successfully fought Zingher in several states where he has attempted to get laws enacted supporting the use of his system.

In Kansas, Sen. Phil Journey, R-Haysville, introduced a bill last year in the Kansas Senate that would have required installation of reverse-PIN alert systems at ATMs, but the measure died in committee.

“It’s just sad,” said Journey, an attorney. “This system makes a lot of sense.”

In Illinois, the industry helped ensure that before such a law was finally passed, in 2003, it had the wording changed so that banks weren’t required to use the system but were merely allowed to — an option they already had.

The industry says it doesn’t want the system because of concerns that the stress of being robbed could lead to hesitation or botched withdrawal attempts as the customer tries to tap in the reverse-PIN, perhaps prompting more violence from the robber.

“The banking industry is in favor of any effective means of making ATM customers safer,” said John Hall of the American Bankers Assn., based in Washington. “We just question whether this is an effective means. There are questions as to whether the customer could remember the PIN backward under duress.”

Lack of information

Zingher alleges that the real reason is that the banks don’t want to admit that ATM robbery is a growing problem that’s being hidden by incomplete crime data collection.

The industry has estimated that there are just 3,000 to 4,000 ATM holdups a year, a tiny sliver of the nation’s roughly 12 billion total ATM transactions each year. But no one can prove or disprove those low ATM crime figures, because they’re lumped in with all other types of bank robberies when the FBI compiles its annual data.

What experts do know is that bank robberies as a whole are up significantly in the past two decades — the same period of time that ATM usage has exploded in society.

“It’s possible … that a large part of the substantial increase in bank robberies is due to ATM robberies. … Oh, absolutely,” said Scott Decker, a professor of criminology and criminal justice at the University of Missouri at St. Louis.

Bank robberies as a whole have ranged in the past 15 years between 8,000 and 12,000 a year, according to FBI data — meaning the bank industry’s estimate of 3,000 to 4,000 for ATM robberies would account for well under half the total bank robberies. Some experts find that low ratio unlikely, given that ATM customers are such easy targets compared with robbing a bank lobby.

Robbers offer insight

Decker co-wrote the book “Armed Robbers in Action,” in which numerous convicted bank robbers were interviewed about their techniques and some were asked to show the authors how they cased targets for their crimes.

“Almost all of them took us to ATMs,” said Decker, “including, for me, somewhat chillingly, an ATM that I had frequented, and they pointed out all the wonderful places you can hide while waiting to jump out.”

Journey, the Kansas senator, has another bill pending in conference committee that would establish a new class of crime for ATM robberies. The bill would do more than increase the potential sentences for those convicted of such crimes, he said.

“This will give us a way to push these violations into a different category, and to quantify how many of these crimes are happening in Kansas,” he said last week. “Once I get the quantification, then I’ll reintroduce it (the reverse-PIN bill) — hopefully in a couple years, once I get the proof.”

Zingher said such data would prove the banking industry was grossly underestimating the extent of the problem.

Hall, the American Bankers Assn. spokesman, said his group wasn’t opposed to such data collection. But he said the group had concerns about how such data would define ATM robberies, which can sometimes take place after the victim has already gotten cash and stepped away from the machine.

“When is it an ATM crime and when is it a mugging?” Hall asked.

Working under stress

The more basic question remains about psychological responses to threat. Experts differ on whether the very concept of Zingher’s invention is asking too much of robbery victims under duress.

“When you first described this,” Decker, the UMSL criminologist, told a reporter last week, “I tried to think of my PIN number backward, and I had a hard time — and you’re not holding a gun to my ribs.”

But Richard Wetzel, a psychologist at Washington University, noted that no psychological generalization fit every crime victim.

“I would think many people would be able to do it, even if some couldn’t,” Wetzel said. And public knowledge of the system, he said, “would deter a few crimes. I don’t know that it would have a down side.”

Zingher’s system wouldn’t require any changes to the ATM terminals themselves but would require reprogramming the relatively small number of computers that actually run those terminals nationwide. Zingher estimated last week that it would mean adding his program to “50 or 60” main computer systems nationwide at a cost of about $10 million.