It could tell you who a masked protester was based on the blood they left behind on a rubber bullet left on the scene, or who sent a mailed-in tip to a newspape

It could tell you who a masked protester was based on the blood they left behind on a rubber bullet left on the scene, or who sent a mailed-in tip to a newspaper based on saliva on the envelope. Just as DNA can help you find who did a criminal act, it can track down who did a political act.