JUSTICES LOOK AT HEAT-SEEKER'S ABILITY TO PIERCE THE HOME

WASHINGTON, 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 hourlong argument was whether use of a thermal
imager by the police is a search that, no less than an actual entry into a
house, requires a warrant. The underlying question was how the Constitution
should take account not only of changing technology but also 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 any reasonable expectation of privacy.

In the case today, Kyllo v. United States, No. 99-8508, the lawyer for an
Oregon man convicted of growing marijuana in his home argued that the
police engaged in an illegal search by using a thermal imager to detect the
distinctive heat pattern made by the high-intensity lights that are often
used for marijuana cultivation. 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," Mr. Lerner 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 people did 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."

Justice Breyer said the question 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."

"Where you're walking in front of the window," he continued, "the answer is
no. Where you're walking in front of the window and people pick it up with
binoculars — every bird-watcher 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."

Justice Breyer said it was at least open to argument whether people had a
valid expectation of privacy that when they took a long hot bath, that fact
would not be disclosed to the world by the use of a thermal imaging device.

Mr. Dreeben replied that while the device can detect heat, "it will not
tell you what's going on inside the house."

Justice Breyer was not satisfied. "It'll just tell you it's hot in there,
which happens to be just the thing they want to know," he said. "They want
to know if it's hot or if it's cold."

Mr. Lerner, representing the defendant, Danny Lee Kyllo, also came in for
tough questioning.

"Why don't your reasonable expectations of privacy include technology?"
Justice Antonin Scalia wanted to know. Inasmuch as there are thermal
imagers in the world, why not expect people to guard against them just as
"you pull your curtains if you want privacy because you know people have
binoculars," Justice Scalia said.

"The burden," Mr. Lerner said, "really is improperly placed on the citizen
to anticipate what type of technology the government may come up with."

Justice David H. Souter asked: "Are you saying, in effect, that if thermal
imaging becomes very common and every school kid has a $5 thermal imager,
that at that point it really would be unreasonable not to expect that the
government was going to use it to figure out what's going on in the house?"

Mr. Lerner said the court would then have to step in just as it has to
prevent indiscriminate use of wiretapping, a technology that everyone knows
is available yet is still regarded as an unconstitutional invasion of
privacy except in limited circumstances.

Mr. Lerner's client entered a conditional guilty plea while challenging the
use of the thermal imager. He first won his case before the United States
Court of Appeals for the Ninth Circuit, in San Francisco, but the appeals
court changed its mind and issued a new opinion after one of the original
members of the three-judge panel retired. Mr. Kyllo served a month in jail
on his marijuana conviction.

The court issued a decision today in another Fourth Amendment case, ruling
8 to 1 that police officers who have probable cause to search a home for
easily destroyed contraband can keep a suspect from entering his own home
during the brief time it takes to get a search warrant.

The decision, Illinois v. McArthur, No. 99-1132, overturned a ruling by an
Illinois appellate court that found the detention to be a seizure that
violated the Fourth Amendment. Justice Breyer wrote the decision,
concluding that the brief detention met the Fourth Amendment's test of
reasonableness.

Justice John Paul Stevens dissented, saying the Illinois court correctly
"placed a higher value on the sanctity of the ordinary citizen's home than
on the prosecution of this petty offense."

The offense was possession of drug paraphernalia and a small quantity of
marijuana, both misdemeanors under Illinois law.