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The Debunker: Can You Alert the Police by Entering Your Bank PIN Backwards?

by Ken Jennings

October is Crime Prevention Month, says the National Crime Prevention Council, and would the nonprofit that brought you McGruff the Crime Dog lie to you about crime prevention? In honor of the occasion, we've decided to shine the hard light of truth on the underbelly of the criminal underworld. As a Jeopardy! superhero, Ken Jennings doesn't fight crime—just misinformation about crime. He'll be here all month debunking felonious falsehoods and misdemeanor myths.

The Debunker: Can You Alert the Police by Entering Your Bank PIN Backwards?

Say you're held up by a ne'er-do-well while using a bank machine, or forced by a mugger to accompany him to an ATM and withdraw the maximum from your bank account. Wouldn't it be great if you could try the thing that those chain e-mails say you can do? According to the rumor, you could enter your security number in reverse, a distress signal like flying the American flag upside-down. This would alert the police, who could swoop in and apprehend the card-confiscating scofflaw.

The Debunker

Well, this is actually a technology that exists! A Chicago lawyer named Joseph Zingher patented the "SafetyPIN System" in 1998, which would trigger a silent alarm if users entered their PIN backwards. State legislatures in Illinois, Georgia, and Kansas took up the cause, proposing laws that would require banks to implement crime-stopping technology like Zingher's.

But here's the problem: there's not a single ATM in the world that currently uses this ingenious solution—for pretty good reason, as it turns out. When Congress had the Federal Trade Commission analyze the benefits of ATM distress signals in 2010, the FTC found that technology like SafetyPIN might not actually prevent or deter crimes (what are the odds that police would actually get to the scene in time?) and may even increase the risk of violence (if, for example, a nervous victim is obviously fumbling the PIN). Then there are logistical issues: the cost to implement the technology, the down sides of false alarms, and so forth. To me the biggest logistical detail to unravel is this: how do we protect people with palindromic PINs? Their real PIN is the same as their reversed emergency code, making them the real forgotten victims of this little scheme.

Quick Quiz: What is the most common four-digit security number, accounting for 10.7% of the world's PINs?

Ken Jennings is the author of eleven books, most recently his Junior Genius Guides, Because I Said So!, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at or on Twitter as @KenJennings.