Before escaping his captors on foot, the man who was carjacked by the Boston Marathon bombing suspects was forced at gunpoint to withdraw money from an ATM. Had he possessed the knowledge and presence of mind to enter his PIN in reverse, some believe, the machine would have automatically notified the police that he was doing so under duress and officers would have been dispatched.

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It's simply not true. Pure bunk. Don't even bother trying to recite your PIN backward (I needed a pen and paper anyway).

That such a bad idea has become an urban legend worthy of a Snopes.com debunking is nowhere near as remarkable, however, as the fact that Congress and multiple state legislatures have actually considered making it law.

From Snopes:

This seemingly helpful heads-up began circulating on the Internet in September 2006. ... The Credit Card Accountability Responsibility and Disclosure Act of 2009 compelled the Federal Trade Commission to provide an analysis of any technology, either then currently available or under development, which would allow a distressed ATM user to send an electronic alert to a law enforcement agency. The following statements were made in the FTC's April 2010 report in response to that requirement: FTC staff learned that emergency-PIN technologies have never been deployed at any ATMs. The respondent banks reported that none of their ATMs currently have installed, or have ever had installed, an emergency-PIN system of any sort. The ATM manufacturer Diebold confirms that, to its knowledge, no ATMs have or have had an emergency-PIN system. (5 years ago they said the iPhone would flop. Now?) Ergo, there aren't and haven't ever been "reverse PIN" technologies despite Internet circulated claims dating to September 2006 that anyone being robbed at an ATM simply had to enter his or her PIN in reverse to summon help. Moreover, said that FTC report: The available information suggests that emergency-PIN and alarm button devices: (1) may not halt or deter crimes to any significant extent; (2) may in some instances increase the danger to customers who are targeted by offenders and also lead to some false alarms (although the exact magnitude of these potential effects cannot be determined); and (3) may impose substantial implementation costs, although no formally derived cost estimates of implementing these technologies are currently available.

I'd add as No. 4: Such a system would undoubtedly encourage the use of simple PINs that would be easy to remember in reverse ... and for identity thieves to exploit.

And those who resisted that temptation would be a different pickle.

Finally, there is the problem of ATM customers' quickly conjuring up their accustomed PINs in reverse: Even in situations lacking added stress, mentally reconstructing one's PIN backwards is a difficult task for many people. Add tothat difficulty the terror of being in the possession of a violent and armed person, and precious few victims might be able to come up with reversed PINs seamlessly enough to fool their captors into believing that everything was proceeding according to plan. As Chuck Stones of the Kansas Bankers Association said in 2004: "I'm not sure anyone here could remember their PIN numbers backward with a gun to their head."

My pen and paper would have been a dead give-away ... perhaps literally.