Heat Image on Infrared Scope Led to Hiker’s Body

Last week, Barbara St. John learned that the body of her only child had been found by authorities at the bottom of a ravine in Angeles National Forest. With that news, one of her most terrifying fears evaporated.

Blayne Marie St. John, a student at the University of California, Irvine, had disappeared into the parched, treeless hills on the afternoon of Aug. 30. As the search for the 19-year-old continued for days, her mother worried that the girl’s body would never be recovered.

“I didn’t want her out in the night air anymore,” St. John said. “I wanted her in where it is safe. I am very relieved; I know she is safe and warm now.”

Authorities said they might never have found St. John, who died of heat stroke, but for the help of an infrared scope. The device, attached to the outside of a Los Angeles County Sheriff’s Department helicopter, was credited with spotting the body, which was hidden under a thicket.

A Glass Eye

The $60,000 device, called the “forward looking infrared,” or FLIR, has the general appearance, shape and size of a volleyball. It weighs 120 pounds and has a glass eye that searches the ground to produce images on the cockpit’s television monitor.

On most nights, the FLIR is used to spot criminal suspects lurking in doorways or hiding in trees. But since its debut in January, 1986, the device also has been used in about a dozen cases to find hikers lost in the rugged mountain terrain that encompasses 55% of Los Angeles County’s more than 4,000 square miles.

Generally, strayed hikers are found within one or two hours of their disappearance, officials said. The infrared equipment is dispatched for those wilderness searches that have proved fruitless.

The device locates people by detecting the heat emanating from objects on the ground. The hotter the object, the brighter it glows on the small screen.

Images are projected onto the screen as an operator in the helicopter manipulates a toggle stick guiding the FLIR orb. Even with the helicopter flying 500 to 800 feet high, the FLIR can spot an object as small as a rabbit.

“It’s a very neat tool for us,” said Sgt. Randy Bresnick, a helicopter pilot. “We can survey all kinds of things without letting people know we’re surveying them.”

By tracking the heat, the operator can detect whether something has recently moved, or has been stationary for some time.

As shown in a Sheriff’s Department instructional film, the FLIR spotted a couple leaning against a lifeguard station on a beach. When the pair walked away, the wall still glowed dully from their body heat. With the FLIR, a law enforcement officer also can determine whether a car was recently parked by checking how much heat is being thrown off by the engine.

“A guy may be hiding in the next yard. Without the FLIR we’d never find him,” Bresnick said.

In the past, the device has spotted suspected rapists and a victim hiding in bushes. It once led to the capture of a sheet-metal thief by pinpointing the suspect’s vehicle--the only one with a hot engine. The thief was hiding under it.

Lost hikers, however, pose a special problem for the FLIR, said Sheriff’s Deputy Tony Pachot, who located St. John’s body last Wednesday morning. Mountainous regions are too dangerous for flying a helicopter at night, but that’s almost exclusively when the device is used by the Sheriff’s Department.

“In the daytime, it’s not very effective,” Pachot said.

That is because nearly everything radiates heat absorbed from sunlight. For instance, it would be difficult to spot a person sitting on a hill during daylight because the grass, rocks and trees also would be emitting heat, he said. Images on the television screen would be obscured by a white glow.

That problem was encountered the first time the infrared equipment was deployed to find St. John on the evening of Aug. 30. The hills were still baking hot--preventing the helicopter crew from spotting her.

The crew tried again at sunrise Wednesday after two days of ground searches failed. Pachot said he was looking for caves, thinking she might have sought refuge in one, when the infrared device spotted a cool area at the base of a tree. On the screen, the lifeless body looked like it might be a rock, but it was emitting slightly more heat than the nearby rocks, which had been cooled by the night air.

“We went down for a closer look, and in fact it was the victim,” Pachot said.