High-Tech Peeking Requires Warrant

The landmark ruling came in the case of an Oregon man who was arrested for growing marijuana in his house after police scanned it with a "thermal-imaging" device. The ruling will echo throughout the 21st century as police gain access to ever more sophisticated surveillance tools.

Conservative Justice Antonin Scalia, writing for the narrow majority, quoted from the high court's own precedent: "We have said that the Fourth Amendment draws 'a firm line at the entrance to the house.'

"The Fourth Amendment bans 'unreasonable' searches and seizures. That line, we think, must be not only firm but also bright - which requires clear specification of those methods of surveillance that require a warrant."

Scalia acknowledged that in the Oregon case, a videotape of the thermal imaging did not indicate a serious invasion of privacy.

"While it is certainly possible to conclude from the videotape of the thermal imaging that occurred in this case that no 'significant' compromise of the homeowner's privacy has occurred," Scalia said, "we must take the long view, from the original meaning of the Fourth Amendment forward."

Nevertheless, Scalia said, the police stepped over the line.

"Where, as here, the government uses a device that is not in general public use, to explore details of the home that would previously have been unknowable without physical intrusion," Scalia said, "the surveillance is a 'search' and is presumptively unreasonable without a warrant."

Scalia was joined by liberal Justices David Souter, Stephen Breyer and Ruth Bader Ginsburg, and fellow conservative Justice Clarence Thomas.

Liberal Justice John Paul Stevens dissented, joined by conservative Chief Justice William Rehnquist, conservative-moderate Justice Sandra Day O'Connor, and moderate-liberal Justice Anthony Kennedy.

The police recorded observations "made with a fairly primitive thermal imager that gathered data exposed on the outside of [a defendant's] home, but did not invade any constitutionally protected interest in privacy," Stevens said. "Moreover, I believe that the supposedly 'bright-line' rule the court has created in response to its concerns about future technological developments is unnecessary, unwise and inconsistent with the Fourth Amendment."

In the case that brought Monday's landmark ruling, federal officers were led to the home of Danny Lee Kyllo in Florence, Ore., in 1992 because his divorced wife had been arrested by state law enforcement on drug charges. Kyllo and his former wife occupied two of the apartments in a triplex building.

An agent from the U.S. Bureau of Land Management asked an Oregon National Guard staff sergeant to take a thermal reading of Kyllo's dwelling.

While seated in a parked car on a public street, the sergeant used an AGEMA Thermovision 210 thermal imaging device to scan the triplex. The imager detects heat escaping from a house. The staff sergeant determined that Kyllo's building was giving off a lot more heat than neighboring buildings, court records said.

Using the information provided by the staff sergeant, the federal agent persuaded a U.S. magistrate to issue a search warrant for Kyllo's home. A subsequent search discovered an indoor marijuana growing operation, firearms and drug paraphernalia, again according to court records.

Kyllo was indicted on one count of growing marijuana, and entered a "conditional" guilty plea in U.S. District Court. Under an agreement with the prosecution, the plea would stand only if an appeals court failed to suppress the evidence from the thermal imager.

Although the case went up and down the appeals court ladder twice, the appeals court eventually decided to let the evidence stand, saying that Kyllo had failed to establish that he had a reasonable "expectation of privacy" on the heat emissions from his home.

Kyllo "made no attempt to conceal these emissions, demonstrating a lack of concern with the heat emitted and a lack of subjective privacy expectation in the heat," the appeals court said.

The Supreme Court heard argument in the case last February. Monday, the justices reversed the appeals court, and sent the case back down for a new hearing.

(No. 99-8508, Kyllo vs. United States)