Depending on where you live, you may find that even local corner stores have sections that are kept under lock and key. Over-the-counter drugs and even toys often end up under "please ask for assistance" supervision. It can be frustrating to have to get a clerk to help you get your cold medicine, batteries, or the newest pack of trading cards, but it makes sense. From surveillance technologies to exploding ink security tags to simple lock-and-key access, businesses are doing what they can to protect their goods and their customers—and to help cut down on incidences of petty theft.
A Scientific Approach
In the Netherlands, local businesses have adopted a crime-prevention system that puts science on the front line of both deterrence and tracking. Fast food restaurants like McDonalds are among the businesses that have installed DNA mist systems. When activated, the system silently alerts police to criminal activity and "marks" the thief with an invisible mist of DNA. Businesses using the system post signs that indicate the presence of DNA systems: "You Steal, You're Marked."
This mist, visible only under ultraviolet light, is so fine that someone being sprayed may not even realize that he or she has been "marked." The mist, however, contains DNA markers that link it to the specific location of the spray system—making it possible to link a criminal to a specific crime based on DNA markers. If apprehended, a simple UV wand may reveal the tell-tale mist. A suspect's presence at a crime location can then be confirmed by matching the mist DNA to its unique location.
For the science-minded—or the armchair detective—the mist-based system raises questions and many "what-ifs." What if the thief goes straight to a public bathroom and changes clothes? What if the thief takes a shower? What if a bunch of bystanders are sprayed? What if the spray doesn't adhere to certain substances or kinds of clothing? There are plenty of questions, any of which you could turn into the beginnings of an independent science project, but reports suggest that businesses using the DNA mist systems have seen a decrease in criminal activity. In part, authorities suggest, the success of the DNA mist system is that its presence alone works as a deterrent.
DNA mist systems are in use in a handful of European countries, and media coverage suggests they may appear in the US soon. Reading about this system brings up one obvious question: why use DNA? Why not use some other synthetic chemical? The answer lies in the versatility and configurability of DNA. Not only is it inexpensive to make large quantities of synthetic DNA, but DNA can be "programmed" to contain an unlimited number of unique tags. Every store in a city could have a unique mist-system with DNA markers that could lead the police straight to their door if a suspect showed up covered in mist linked to their location. This kind of widespread site-specific and distinct crime marker wouldn't necessarily be possible with other chemicals. Plus, forensics labs are also accustomed to handling and analyzing DNA. The systems are already in place to read and evaluate DNA.
And would-be criminals know it, which increases the power of the warning: "You Steal, You're Marked."
Students interested in DNA and curious about the properties of DNA, and the infinite customization possible with DNA's 4 base pairs, can get an introduction to understanding DNA fragments in this Science Buddies project idea:
- What Makes a DNA Fingerprint Unique? (Difficulty: 4-6 )
Students with access to a lab—and more time— can take their exploration a bit further in this project idea:
- Who Done It? DNA Fingerprinting and Forensics (Difficulty: 8-10)