The dark side of DNA

The Times has an excellent article on "surreptitious sampling," the police practice of collecting DNA samples from suspects without their knowledge (and without a warrant). In a typical case, the cops follow a suspect who may happen to be smoking a cigarette or drinking a soda. The cigarette butt or soda can collects trace amounts of saliva, which contains the suspect's DNA. The suspect throws the butt on the ground (with his DNA on it), the cops pick it up, and then they have a sample.

Prosecutors love the practice, defense attorneys hate it. I don't know how I feel, to be honest. The ordinary rule is that if a person throws something away, they lose any expectation of privacy they may have in the item- no probable cause. The ordinary rule, however, was for objects. In these cases, what the cops want is the traces of DNA left on the object, something that the suspects may not have even realized they were leaving behind. I honestly don't know what to make of this right now, but I am damn intrigued.