[tesq]

"Passive" scanners violate the 4th amendment just as much as "invasive" ones.

Kyllo vs United States determined that thermal imaging without a warrant was a search and constituted a violation of a person's 4th amendment rights. "Off the wall" and "through the wall" surveillance are one and the same.

[briandear]

So would the NYPD be subject to a 4th Amendment challenge? I would think the case you cite would say so.

[tesq]

I'm not a lawyer, but I'd say it would hinge on how much the NYPD publicly releases about how they're used in investigations. I expect that if they're used in criminal or FISA Court suits, evidence will be obfuscated, classified or omitted.

In Kyllo's case, a person's home has a much better expectation of privacy from invasive surveillance than one's person and property in public. If it becomes public that people's homes are being searched without warrants, then I'd assume that they'd rightly be challenged.

It would be interesting and probably frightening to see how invasive surveillance of a person and property, in what might be considered 'public' space, would be challenged in court.