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Tuesday, 12 June, 2001, 07:45 GMT 08:45 UK
Thermal imaging 'constitutes search'
Danny Kyllo
Danny Kyllo was arrested in 1992
The use of thermal imaging to detect illegal activity without entering a home is a "search" for which police must obtain a warrant, the US Supreme Court ruled on Monday.

In a 5-4 decision, the court ruled that police violated the rights of a man from Oregon in the Pacific North West by using a heat-seeking device without a warrant to determine if he was using high-intensity lamps to grow marijuana indoors.

The question we confront today is what limits there are upon this power of technology to shrink the realm of guaranteed privacy

Supreme Court Judge Antonin Scalia
The court said the case went to the heart of the constitution's Fourth Amendment, guaranteeing "the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures".

Danny Kyllo of Florence, Oregon, was suspected of growing marijuana, but authorities obtained a search warrant only after using evidence from the thermal-imaging device suggesting that he used high-intensity lamps.

The ruling is a setback for the US Justice Department, which argued such use of a thermal imager was not a search and was not covered by the privacy protections.

Protecting privacy

Any evidence obtained from the interior of someone's home, which would, without the use of technology not generally available to the public, have needed physical intrusion, constitutes a search, Justice Antonin Scalia wrote.

"It would be foolish to contend that the degree of privacy secured to citizens by the Fourth Amendment has been entirely unaffected by the advance of technology," Justice Scalia wrote.

"The question we confront today is what limits there are upon this power of technology to shrink the realm of guaranteed privacy," he wrote.

The decision overturned a lower court ruling that thermal imaging was not a "search" under the constitution because it was a non-intrusive device and did not show people's activity or record conversations.

Allowing the search, the justice wrote, "would leave the homeowner at the mercy of advancing technology - including imaging technology that could discern all human activity in the home".

Previous rulings

Mr Kyllo was arrested in January 1992 and charged with growing marijuana at his home.

Police had trained a thermal imaging device on his home and found signs of high-intensity lights.

Using those images, electricity records and an informant's tip, police got a warrant and searched Kyllo's home.

Last year, the Supreme Court ruled that police must get bus passengers' consent or a search warrant before squeezing their luggage to see if drugs might be inside.

The court also requires a warrant to put an eavesdropping "bug" in someone's home or in a telephone booth.

But the justices have said police do not need a warrant to go through someone's rubbish left on the pavement, fly over a garden to see what is on the ground or put a tracking device on a car to make it easier to follow.

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06 Mar 01 | Americas
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