Pot may be legal in Colorado, but that doesn’t mean the state has no illegal pot. Legal growers have illegally sold cannabis across state lines, and illegal growers can forge a paper trail to enter the legal market. It’s a problem for law enforcement, which needs to combat this gray market to keep the state’s $1.5 billion cannabis industry on the right side of federal compliance. Starting this summer, the state could be able to identify all aboveboard cannabis. Using technology previously employed to track premium American cotton from gin to shirt, growers spray their legal plants with DNA that acts like a molecule-size encrypted bar code. By bonding to the plant—but not changing its DNA—the tag withstands processing and even shows up in refined products such as oils and edibles. Dispensaries and local law enforcement can then feed a tiny bit of a product into a reader, the SigNify, that confirms the farm, strain, and permit number.



The outer fins create a heat sink for the hot–cold polymerase chain reaction (explained at right) that multiplies the DNA tag. SigNify

Biotech company Applied DNA Sciences produces the tags. “Think of the DNA as a content carrier,” says Jim Hayward, company CEO. The tags are engineered to embed up to 250 bits of identifying information in the sequence of DNA nucleotides. This allows for billions of potential DNA signatures for plants and manufacturers. To avoid harming or affecting the plants, the tags are dissolved in water and measure in the parts per trillion, and the spray uses minimal moisture to eliminate risk of mold.

Graham Murdoch

When a sample is placed in the SigNify, the device uses a polymerase chain reaction to reproduce the tags for easy identification. Because the contents of the tags are secure—Applied DNA employees can access only portions of them—they can’t be copied. Which means counterfeits can’t be made, and fewer illegal products can make it into a legal system.

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