Rob Ward keeps baby wipes, canned soup, and bottled water in his truck. “If I need a bath or a meal, there it is,” he explained in a Walker, Louisiana Waffle House. Calls can come at anytime, and his truck remains loaded, his bag packed.

Today is a rare day off from both of his jobs: a nine to five at a printing company and volunteer work looking for dead bodies with his Australian shepherd, Niko. Ward and Niko are one of approximately 500 volunteer cadaver dog-handler pairs across the country who assist law enforcement in recovering human remains.

Ward remembers a call a few years back: a missing female, suspected homicide. He put 1,500 miles on his truck over the course of a month searching for her, but they found nothing. Then, on a scorching day in a wooded field, the humidity weighing on Ward and 15 law enforcement officers, Niko started running. After a few yards, he abruptly sat down. He had found part of a pelvis and a leg, all bone, unburied. Soon they found most of a full skeleton.

“That one has stayed with me for some reason. I knew the victim’s name,” Ward said. “You take the emotions, and you set it aside, because you’ve got a job to do. You deal with the grief, or the anger, afterwards.”

Facebook Twitter Pinterest Lisa Higgins addresses other members of the Louisiana Search and Rescue Dog Team before the group’s training session. Photograph: William Widmer/The Guardian

Even big counties usually don’t have enough annual missing persons to justify the time and expense it takes for police to train a cadaver dog. Therefore, the majority of cadaver dog teams nationwide are volunteers. They are doctors, teachers and stay-at-home moms, and their dogs.

A dog’s sense of smell is stronger than a human’s by orders of magnitude. One police officer gave this metaphor: if you walk into a house where someone is cooking gumbo, you can smell that immediately. But a dog smells the garlic, chopped onions, and each kind of fish going into the pot. Death, much like gumbo, emits a bouquet of smells. One scientific study found cadaver dogs were approximately 97% accurate overall in picking out a square of carpet that had been contaminated with the smell of a human corpse.

You take the emotions, and you set it aside, because you’ve got a job to do. You deal with the grief, or the anger, afterwards

Any dog breed can be used, though classic working breeds such as labradors or shepherds are common. Any person (excluding those with a criminal background) can become a handler, but many don’t get through the grueling training. The teams that do achieve certification become a rare few civilians allowed to participate in criminal investigations, including murders, kidnappings and serial crimes. Why the handlers volunteer – and why police let them – tests the boundaries of community service and law enforcement.

St Tammany parish in south-eastern Louisiana is peppered by swimming holes, lakes, rivers, creeks and bayous. Live oaks, Spanish moss and various wildlife flourish along the waterways within St Tammany. With over 200,000 residents and 279 square miles of navigable water, drownings and boat accidents are frequent. Logjams can clog the rivers; strong currents challenge even experienced divers, and the swamps and bayous are home to a handful of alligators (although shrimp can sometimes eat a dead body faster). In the late 90s, this parish led the state in drowning deaths, but that number is down to two or three a year now, according to local police. The St Tammany sheriff’s office has its own K-9s for apprehension, narcotics detection, and tracking, but they do not train cadaver dogs.

For 18 of his 23 years as a police officer, Deputy Chance Wood, 43, has served in the marine unit, rescuing people in distress and recovering the remains of those who have drowned, often with the help of cadaver dogs. “I’ve made more recoveries than I care to count, but I’ve helped more people than I had to recover,” he said.

Facebook Twitter Pinterest Chance Wood steers handler Kirsten Watson and her one-year-old dog, Quest. Photograph: William Widmer/The Guardian

One of the recoveries that a cadaver dog team assisted with back in 2015 was the body of a young mother. While boating with her three kids, the engine failed, sending them over a dam. Two of the children were saved by a nearby teenager; the third child spent almost an hour in an air pocket underneath the boat but survived. The mother, then 31 years old, drowned. She was Wood’s sister.

Wood uses the same word the local cadaver dog handlers use when talking about their work: service. Wood has never told the local dog team the story about his sister. Instead, he expresses his gratitude through service: even on some of his days off, he pilots a boat for team training. “It amazes me, the dedication and just the drive,” he said of the volunteer teams.

On a sunny Saturday in January, a group of dog handlers arrive at 9am near the 36,000-acre Bogue Chitto refuge. The handlers come from New Orleans, Walker and as far as the Baton Rouge area. They swap homemade cookies and talk about their vacations. Out of the cracked windows of their parked cars, nearly a dozen dogs bark in excitement.

Every Saturday, regardless of the weather, the team trains around Louisiana, sometimes from sunup to sundown. The newest member is Kirsten Watson, a petite woman in her 40s who somehow manages to control her 77lb German shepherd. She has been training for about a year, while some of the veteran handlers have decades of experience.

Facebook Twitter Pinterest Ann Dugas and her nine-year-old dog Sundance after a water search exercise. Photograph: William Widmer/The Guardian

James Todd, whom the team calls “Doc”, is an orthopedist who could no longer perform surgery after a hunting accident blinded him in one eye, but he’s been able to use his medical skills in the field – he once administered first aid on an Alzheimer’s patient they located who had been presumed dead. Pat Brown worked with dogs as a New Orleans police officer; when he retired, he found it hard to enjoy the free time. “I was bored, aggravating my wife. So she went and bought a dog and said ‘find something to do,’” he said. Ann Dugas works part-time for Toyota, when she isn’t out with one of her six working dogs. Wood is here, too, piloting the boat on the Pearl River canal.

Later this afternoon, Wood will take teams on the water, the dogs’ paws clenching the edges, until they pick up on the smell from an underwater air canister scented with human remains. The dogs learn to alert on the water based on odor that comes through air bubbles (dead bodies emit gases that gurgle to the surface).

Lisa Higgins starts herding the dogs and their handlers toward the first exercise: a speed drill with autopsy rags. Higgins, whom everyone calls “Miss Lisa”, founded the Louisiana Search and Rescue Team (LaSAR) 30 years ago and has responded to upwards of 400 searches. She’s the team trainer now, and her manner of answering questions and gently correcting the handlers brings to mind the patience of a school teacher. She was the first female mounted police officer in Pearl River in 1978. Seeing a need for the dogs in her search and rescue work with the police, she started a volunteer cadaver dog team with her daughter.

Left: Lisa Higgins kneels next to her German Shepard during a training session she led for the Louisiana Search and Rescue Dog Team in rural St. Tammany Parish. Right: Kirsten Watson stands next to her one year-old German Shepard Quest. Watson is training her dog to detect human remains. Left: Lisa Higgins kneels next to her German Shepard during a training session she led for the Louisiana Search and Rescue Dog Team in rural St. Tammany Parish. Right: Kirsten Watson stands next to her one year-old German Shepard Quest. Watson is training her dog to detect human remains.

Right: Pat Brown kneels next to his three year-old dog Charlie. Brown has trained Charlie to detect human remains, and his sister Adain to specialize in "live hunts Left: Ann Dugas kneels next to her dogs Sundance (L, 9) and Oakley (2.5). Both dogs are trained to detect human remains. Right: Pat Brown kneels next to his three year-old dog Charlie. Brown has trained Charlie to detect human remains, and his sister Adain to specialize in “live hunts.”

As she opens a plastic case of training materials, the smell of death becomes obvious. This team trains on bones, blood, teeth, skin, placenta, autopsy rags and blood-smeared weapons, much of which comes from donations to science. The bones are on loan from a professor who worked with Higgins on a five-year study about cadaver dogs. Access to materials like bones or flesh are restricted in most states, and handlers have to prove their credentials. In Tennessee or North Carolina there are “body farms” to train dogs on full corpses.

Tails are wagging and the dogs pull on their leashes. On one drill, the dogs must find a container of gauze stained with human blood, hidden a few hundred yards into the woods. When the handlers say “seek” or “go find it,” the dogs take off, running in wide circles, with their handler traipsing in the woods behind them.

The only sounds during the drill are leaves crunching, the dog’s deep breathing trying to smell everything around her, and Lisa’s quiet corrections to the handler. “Talk less,” she’ll say. “Trust your dog.” All but the most stubborn handlers respond with “Yes ma’am.” The dogs are trained to keep looking until they’re not just close but inches away – and that’s when Messi barks. She found the gauze, hidden in a rotting tree stump.

Facebook Twitter Pinterest A glass jar filled with an ‘odor sample’ – in this case a rag soaked in bodily fluid – that Lisa Higgins uses in training courses for the Louisiana Search and Rescue Dog Team. Photograph: William Widmer/The Guardian

After a cadaver dog is fully trained – which can take as long as two years – they are meant to have the intelligence of a seven-year-old child. They understand dozens of words and find human remains across a variety of environments. Law enforcement recognizes about half a dozen different certifications, but no single entity regulates the teams.

Dogs respond to their handlers’ emotions, which is why the handlers must show only joy when their dog finds something. That’s not always easy, especially when it comes to murder, dismemberment or the death of children. Ann Dugas has been doing this work for more than 20 years, and she can usually compartmentalize. Tears came to her eyes as she described finding a 14-year-old drowning victim more than a decade ago, at a time when she had a child the same age. After her dog indicated his location and police took over to pull the body up, she walked down the road and cried.

Higgins’s first find nearly 30 years ago was a drowning victim lodged four feet under water and three feet under sand. Now 66, with salt-and-pepper hair, Higgins seems used to being underestimated. She’s not one to brag, so it took a few days of being on the trail with her to learn about the serial killers she’s helped put away, as well as her frequent collaborations with the FBI.

About 10 years ago, she flew to Alaska for a murder case. Little did she know at the time, but the serial killer, Joshua Wade, watched as she and police searched his house. Higgins’s dog was able to indicate the exact clothing Wade was wearing when he was in close proximity to the remains of a neighbor he shot, execution-style in the head. Wade has since admitted to four other murders and is serving a life sentence.

'Talk less,' she’ll say. 'Trust your dog.'

Many handlers and experts are women. During searches in the 1990s, Higgins encountered resistance from the male-dominated world of law enforcement. One diver said he wouldn’t jump in the water because “some lady’s dog said so”. Gesturing around us, she said: “You’re in the south. They did not want women.” She added, laughing, “but it was their mistake”. That reluctance has changed, in part because of national tragedies in which cadaver dogs were used, such as 9/11, Hurricane Katrina and California wildfires.

Facebook Twitter Pinterest Snow, a search dog specializing in the location of human remains, locates a sample that the team hid in the woods of rural St Tammany parish. Photograph: William Widmer/The Guardian

Higgins describes Kirsten Watson, the newcomer, as having the perfect combination of talent and drive. Watson, a former animal control officer, recently started training her first cadaver dog, a German shepherd named Quest. After a break for lunch at a roadside barbecue called Hog Heaven, the trainers drove to a second site further up the canal, looking for one of six training burials scattered near the Pearl River. As the sun started to set, Watson climbed a wooded hill with Quest, as Higgins watched a few yards behind. Watson grew frustrated after Quest found the scent and then dropped it, his boundless puppy energy momentarily taking over. Higgins gave minor corrections but reassured Watson that both she and Quest were on the right track.

Watson has a personal stake in this work: in 2015, her father disappeared. He has never been found. Many of the cases these handlers work went cold years before. In a city like New Orleans where police have heavy caseloads, the cold trail of a missing person is not a top priority. That’s where teams like this one come in, following up leads on the weekends, even just to rule something out.

“They need to come home too,” she said of those missing people. “Many times, these people that we’re looking for were discarded like trash – and being able to bring them home to their families – someone’s got to do it.”