ASHINGTON, Feb. 20 — The Supreme Court wrestled today
with how to apply the Fourth Amendment's ban on unreasonable
searches to a technological development the Constitution's
framers most likely did not have in mind: a thermal imaging
device that the police can use from outside a home to detect
patterns of heat being generated from inside.
The specific question in the hour-long argument was whether
use of a thermal imager by the police is a search that requires
a warrant, no less than an actual entry into the house. The
underlying question was how the Constitution should take account
not only of changing technology, but of society's changing
understanding of technology's threat to privacy.
Under the court's precedents, the Fourth Amendment protects
only those expectations of privacy that are "reasonable."
Someone who conducts business in front of an open living room
window, for example, may be deemed to have forfeited a
reasonable expectation of privacy.
In the case today, the lawyer for an Oregon man convicted of
growing marijuana in his home argued that the use by the police
of a thermal imager to detect the distinctive heat pattern made
by the high-intensity lights that are often used for marijuana
cultivation was an illegal search. The police used the
information as the basis for obtaining a warrant to search the
house.
People have a reasonable expectation of privacy in what goes
on behind the opaque walls of their homes, the lawyer, Kenneth
Lerner, told the justices. What the thermal imager captures
"really is molecular information that migrates through our
walls," he said, adding: "If we are now saying that we can
capture that kind of information without a warrant, we can
reduce our whole world to that type of wave and molecule and our
walls mean nothing."
But Michael R. Dreeben, a deputy solicitor general arguing
for the government, said that people do not have a reasonable
expectation of privacy "in the heat that's on the exterior
surface of their walls."
"Heat loss is an inevitable feature of heat in a structure,"
Mr. Dreeben said. "That's why there is an insulation
industry."
Justice Stephen G. Breyer objected that the expectation of
privacy "is not in heat loss, it's in what is going on in the
house."
The question, Justice Breyer said, was whether `'you have a
reasonable expectation that the kind of thing you're doing in
the house will not be picked up by somebody out of the house,
not a law enforcement officer, but just ordinary people."
He continued: "Where you're walking in front of the window,
the answer is no. Where you're walking in front of the window
and people pick it up with binoculars, every birdwatcher has
binoculars. Where they're picking it up with flashlights, every
Boy Scout has a flashlight. Who has a heat thermal device?
Nobody, except a few."
