In January 1995, Macarthur Wheeler and Clifton Johnson robbed a bank in Swissvale, Pennsylvania. However, they had a plan to avoid detection: they rubbed lemon juice on their faces. Their reasoning was that lemon juice can be used to make invisible ink, so surely it would conceal their faces from surveillance cameras as well. They even tested this hypothesis by taking polaroid pictures of each other smeared with lemon juice, and it seemed to work.
Unfortunately, they showed up just fine on the bank's cameras, and they were identified and arrested several months later when the footage of the robbery was broadcast on a local news show.
This odd crime has an interesting postscript. The psychologists David Dunning and Justin Kruger of Cornell University read about it, and it inspired them to start thinking about the problem of stupidity: this being that stupid people often don’t realize they’re stupid. In fact, they think they’re quite smart, which leads them to do incredibly dumb things. This phenomenon (of dumb people not being able to recognize the limits of their competence) is now known as the Dunning-Kruger Effect. In the journal article in which they introduced the concept
, Dunning and Kruger cited the lemon-juice bandits as their inspiration.
Tyrone Daily Herald - Jan 8, 1996
Pittsburgh Post Gazette - Mar 21, 1996