In 1992, a group of students at Johns Hopkins University in Maryland carried out an assignment to rig a gun to fire only when held by its rightful owner. It cost them little more than $2,000.

In the two decades since, the U.S. government has spent millions of dollars on grants for research institutions and gun makers to perfect a personalized gun ― mostly on biometric methods such as fingerprint and grip recognition.

New Jersey passed a law in 2002 mandating that once such a gun becomes commercially available, all guns sold in the state must incorporate the technology within three years.

While champions of personalized guns have long insisted that the technology is within reach, no such gun has made it to the mainstream U.S. market.