Nine hundred feet in the night sky, the State Patrol helicopter circled above a New Hope neighborhood where police were searching for a suspect who had run away, bleeding heavily, after a domestic dispute.

Chief Warrant Officer Greg Burgess flew the chopper, staying in radio contact with the officers below. Co-pilot Dave Latt operated an infrared camera that scanned the snowy terrain, seeing what the naked eye could not.

Latt peered at a screen the size of a small television. It showed the officers and their dog as they would have appeared in an old black-and-white negative, their shapes ghostly white against the dark background. Latt used a big joystick to zoom in on the area, directing the officers on the ground.

Latt and Burgess are experts in the use of infrared cameras that "see" heat emitted from an object, and then store those images on a hard drive as police evidence.

Law enforcers use the leading brand, FLIR Systems, mostly at night. Within minutes, they can find lost people, fugitives -- and, in a relatively recent twist, even houses where the heat from lights used to grow marijuana sends off bright plumes of energy, visible only with the thermal imager. That's led to concerns that the devices give police too much power to snoop on citizens.

Latt and Burgess belong to the Minnesota State Patrol Flight Section, and theirs is the state's only law enforcement agency with thermal imaging.

Each night, the pilots soar above a sea of white, blue and amber lights as they loop around the metro area. They scan police radio frequencies and wait for calls for assistance. Once a day, on average, they get a request from a police agency, from Savage to Detroit Lakes and beyond.

Six pilots and a chief work out of the St. Paul Downtown Airport and two more fly out of Aitkin, Minn., said Lt. Matt Nelson, chief pilot. The patrol has FLIR in three of its four copters, but not in its five planes.

Often, the crews are called on to find the lost, from toddlers to the elderly.

On a chilly night last fall, Nelson and pilot Dave Willar flew to Hubbard County to find a man who had wandered into the woods from a care center. The man, in his 60s, was an Alzheimer's patient with Parkinson's disease. He was wearing only a knit shirt and sweatpants when last seen at dinner time. Officers from 10 agencies had searched for him in the rough terrain as the temperatures dropped to freezing.

Eventually, they called for the thermal imager. The pilots soon spotted the sprawled man.

"We were on scene at 11:29 p.m. and located the subject at 12:18 a.m.," Nelson said.

The man had become trapped under brush, and his core temperature was cooling, said Hubbard County Sheriff Frank Homer.

"The chances would have been minimal of not only locating him, but for his survival, if we did not have the FLIR up and ready to go," Homer said.

The sweeps

Officers say the use of FLIR can quickly "clear" woods and fields. They like to have the helicopters fly over a property during night-time raids to see if a criminal is hiding outside.

Thermal imagers not only help catch a suspect but can protect officers from ambushes, said Sgt. Jason Polinski of the Dakota Drug Task Force.

"It puts you back into control because you know where they're at," he said. "You take the hiding out of it."

Once the pilots spot a suspect, they aim a laser beam at him so other officers can spot him with the help of night-vision goggles. The suspect, of course, has no idea there's a laser circle on his back.

This month, Latt and pilot Dean Grothem joined the hunt for a man accused of robbing a movie theater in Apple Valley. After police arrived at the Lakeville home of the suspect, Davis Powell, 26, he fled barefoot through the snow. Using FLIR to see thermal energy left by his fresh footprints, the pilots tracked Powell.

He appeared on their screen as a bright "hot spot," running and then rolling down snowy hills in his attempt to get away. Powell crawled into a big culvert, but the infrared camera picked up his image through one open end. The pilots directed officers and their dog to the man. Powell was bitten, then arrested.

Two weeks ago, in rural Eureka Township, Dakota County's tactical team raided a suspected methamphetamine lab before sunrise. FLIR video shows how pilots scanned the farmyard and wooded area.

Drug busts

Though most of the missions are to find suspects or lost people, including plenty of hunters, 15 to 20 missions a year involve narcotics officers who get search warrants to fly above a building where they suspect a marijuana farm is operating. The grow lights, humidity and heat make the roofs and foundations glow white.

The pilots then give officers the video evidence that helps them get warrants to conduct ground raids.

The technology cannot see through walls, so it isn't intrusive, authorities say.

But Chuck Samuelson, director of the American Civil Liberties Union in Minnesota, criticizes the use of infrared cameras to spot the huge heat blooms from suspected indoor pot farms. Samuelson said while he supports using FLIR to find lost people, the technology can smack of "Big Brother" watching, with the potential to overreach in investigations.

Samuelson said the use of thermal imaging in choppers also raises a public policy question: Is it worth the cost?

Nelson said the aviation section operates on an annual budget of about $600,000.

Over the years, Commander John Grant of the Dakota County Sheriff's Office has come to know the investigative value of relying on FLIR. He's seen firsthand how thermal imagers make roofs and foundations around indoor pot farms glow white, helping investigators to build cases.

"It's a great tool, I'll tell you that," he said.

Joy Powell • 952-882-9017