DENVER — When homicide detectives have a hard time finding bodies, they often contact a specific group of Colorado scientists. The 45 volunteers are premier experts of clandestine grave exploration.

For more than three decades, NecroSearch International has been helping police on hundreds of homicide cases in Colorado, across the country and around the world.

“It’s really about bringing victims back to their families,” said group president Bruce Yoshioka.

The group was born from a mix of Denver-area law enforcement professionals like former Colorado Bureau of Investigation investigator Tom Griffin. He recognized a need to bring scientists — from more than a dozen disciplines — together to brainstorm the best ways to locate bodies.

Today, many of those scientists are retired like forensic anthropologist Diane France, geophysicist Clark Davenport and geologist Jim Reed. They’ve been part of some of the most high-profile cases in Colorado history.

Much of what they know — and their nickname — is thanks to a specific animal. They’re called “the pig people” because of the research they do at a pigs’ graveyard outside Littleton. The location is where archeologists, botanists, hydrologists and many other smart people do their research.

“With the pigs, it’s the idea of we can go back now decades later,” Griffin said.

What’s learned at the pig graveyard is carried into real-world CSI problem solving. The challenge, however, is pinpointing where to look.

“We know we’re looking for a needle in a haystack,” Griffin explained. “We just need to have that haystack narrowed down.”

France says some of the best ideas come from group brainstorming meetings.

“When we talk about what we do and how we do it … a lot of it is just common sense,” she said.

When police lead the pig people to a specific area, the team may start with an aerial survey. They compare differences in topography from before and after a suspected burial with the help of drone technology.

From there, the NecroSearch team will look at just about everything — from plant life, soil composition, temperature and moisture.

“It could be thermal,” Reed said. “It’s more porous so you’re getting more heat coming out. So thermal infrared is another big trick.”

Everything from ground-penetrating radar to dogs are used to collect evidence and piece together detailed reports for law enforcement. But it’s not all high-tech. There has been success with something as simple as flattened soil and water bottles — finding a Pueblo grave in the 1990s.

“It was obvious — the outline of this grave,” Reed said. “We started digging and there’s a body. I remember driving back from Pueblo, and I was on cloud nine … just thinking this was so low-tech. So simple, and it worked.”

Even the best of the best, at times, cannot find a body. But these volunteers don’t give up. They say every search — no matter the outcome — is worthwhile.

“There is no failure in what we do because even if we don’t find evidence or human remains we can learn something from that experience,” Griffin explained.

NecroSearch International prides itself on helping police while also sharing research at conferences to educate other scientists in search of human remains.

“Last year we had a total of eight cases,” Yoshioka said. “This year, I believe we’re up to 22.”

One of the big recent cases was the disappearance of Kelsey Berreth. Her body has not been found. Even without a body, there was enough evidence to convict her fiancée Patrick Frazee.

On Friday night, FOX31 will take a closer look at the Berreth case and the important role NecroSearch International played in the investigation.