The Long Branch of the Law: Inside the National Park Service's Criminal Investigations Unit

The National Park Service's Investigative Services Branch handles crime in the park system.
The National Park Service's Investigative Services Branch handles crime in the park system.
Courtesy of the National Park Service

Jeff Sullivan watched as the man dug up the grave. It was the mid-1990s, and Sullivan was undercover, posing as a hunter at Channel Islands National Park, a cluster of rugged islands off Ventura, California. Every month or two, Sullivan crossed the water to meet up with a group that escorted tourists looking to hunt sheep and pigs. But Sullivan knew they were really plundering the graves of Native Americans, excavating cultural artifacts as well as bones for resale.

For two years, he returned time and again, seemingly eager to pursue sheep. Finally, one of the guides who considered Sullivan a friend took Sullivan and other undercover agents to a grave that he proceeded to dig up.

The man cautioned them keep quiet. He said disturbing the bones was a "lock-up offense."

It was exactly the kind of demonstration Sullivan had been hoping for. As the man speared the shovel into the dirt, Sullivan, wearing an audio recorder, was gathering evidence. The man and his associates were eventually convicted of illegally disturbing archaeological sites and graves, a violation of the Native American Graves Protection and Repatriation Act.

Sullivan, who testified in court about the case, is still on active duty as an assistant special agent in charge. He is not an FBI agent or a member of any law enforcement agency. For over 35 years, he’s worked for the Investigative Services Branch of the National Park Service, a division devoted to handling criminal activity committed on the staggeringly vast 85 million acres of federally owned land. The ISB routinely investigates animal poaching, missing persons, and homicides. And they do it with only a tiny fraction of the resources and manpower of the large law enforcement agencies.

“Most of us came into the agency thinking we’d just investigate poaching or resource crime, and we do,” Sullivan tells Mental Floss. “But the vast majority are crimes against people. Rapes, homicides, and everything in between.”

Inside the federal parks, he says, “People bring their problems with them.”


When President Ulysses S. Grant signed the Yellowstone National Park Protection Act into law in 1872, he was officially establishing the country’s first national park. Ever since, hundreds of parks, all owned and operated by the federal government, have fallen under the NPS umbrella. The job of the NPS is to preserve and protect irreplaceable environmental assets.

From the start, that’s been a challenge. While the land that makes up Yellowstone was once occupied peacefully by Native tribes, its increasing occupation by the government led to more disruptive activity. In the late 1800s, Yellowstone was ravaged by poachers, squatters, and vandals who had no regard for the ineffectual authority of the park superintendents who doubled as police. In response, the government dispatched the U.S. Army in 1886, stationing soldiers throughout the park to patrol the grounds and deal with problems. When a bison poacher got away with little more than a wrist slap, the public was outraged, and lawmakers established the National Park Protection Act, or Lacey Act, of 1894 to provide more stringent punishment for troublemakers [PDF].

A National Park Service Investigative Services Branch Special Agent is pictured
ISB Special Agents need to feel comfortable working in remote locations.
Courtesy of the National Park Service

While the Army was an effective deterrent against crime, soldiers were not exactly a wealth of park information for visitors. Hoping to create more uniformity in the growing park system, President Woodrow Wilson approved the National Park Service Organic Act in 1916, setting the stage for a fleet of park rangers who could both police and tend to visitors.

Eventually, even the rangers found themselves overwhelmed at times with activity in the park that required more specialized law enforcement attention. Following a riot at Stoneman Meadow in Yosemite in 1970, the Yosemite and Olympic national parks hired criminal investigation specialists to look into serious infractions on park land. Other parks followed suit.

Instead of parks hiring their own individual investigators, the NPS eventually opened the Investigative Services Branch, or ISB, which was given its formal name in 2003. But rangers like Sullivan had made the move years earlier. After starting in the Ozark National Scenic Riverways in the early 1990s, he became one of the first ISB special agents.

“I gradually worked my way into it,” Sullivan says. “After six years on patrol, I became an investigator.”

Sunset on Half-Dome in Yosemite National Park
Yosemite National Park
Brandon_Nimon/iStock via Getty Images

If a serious crime happens on federal park land, the ISB typically has jurisdiction, though that can vary by location. (Some states have proprietary or concurrent rights to a crime scene, meaning they either take it over or work in tandem with the ISB or FBI. The latter two agencies can also work together.) That means a park official’s first call is typically to the rangers, who then contact the ISB, as in the case of the Theodore Roosevelt revolver that was stolen from Sagamore Hill in 1990. (It was recovered 16 years later.)

The ISB, Sullivan says, is contacted when a crime exceeds the threshold for what rangers typically handle. That means calls to address violent crimes, significant acts of theft or poaching, and missing persons. In the Pacific Field Office headquartered at Yosemite [PDF], agents recently addressed a 2017 assault with a deadly weapon and strangulation at a campground in Haleakalā National Park; vandals who smashed Devil's Hole pupfish eggs, a species among the rarest on Earth, at Death Valley National Park in 2016; and a DUI vehicular assault at Olympic National Park in 2017.

Sullivan has seen no shortage of memorable cases—like his run-in with serial killer Cary Stayner, who committed multiple murders in and around Yosemite, including the beheading of park naturalist Joie Ruth Armstrong in 1999. Sullivan saw Stayner driving near the park at the estimated time of the murder. Stayner later confessed to four killings total.

According to Sullivan, what makes the ISB different from other investigative agencies is simple. They’re not a law enforcement agency.

“We’re an agency that does law enforcement,” he says. “There’s a big difference.”

A National Park Service Investigative Services Branch Special Agent examines a crime scene
ISB Special Agents don't have the resources of major law enforcement agencies.
Courtesy of the National Park Service

Unlike the FBI, the National Park Service is not a multi-tiered agency devoted to criminal investigation. The NPS’s main priority is protection of natural resources, meaning that the lone branch devoted to crime—the ISB—is a small part of the machine. There are just 33 special agents covering the entire country in four locations: the Pacific, North Central, Southwest, and Atlantic Field Offices. Each is responsible for multiple parks in multiple states. The Atlantic office alone covers 23 states.

“We expect [agents] to carry the bulk of the load and do the job,” Sullivan says. As a senior officer tasked with hiring, Sullivan says he looks for people who can work well by themselves and don’t mind the solitude that comes with operating in remote parts of the country.

Some agents come, stay for a bit, and realize it’s not a fit. “We live and work at the end of the road,” he says. “If you enjoy the social aspect, the nightlife, it’s not for you.”

Owing to the small staff, there’s no ISB forensic department. Agents rely on state or federal labs, hopefully building a rapport with local forensic analysts in the process. Because the ISB has to share resources, agents might also find themselves coming to the office and then being asked to jump on a helicopter to assist in an investigation three states away.

Moss-covered trees in Olympic National Park
Olympic National Park
dene398/iStock via Getty Images

Sullivan says that there’s a kind of freedom in not having to deal with a lot of bureaucracy. Agents don’t just make arrests and hand the perp off to another department. They often see a case through to the end and into the hands of a prosecuting U.S. attorney, as Special Agent Beth Shott did when she successfully investigated the 2012 death of Toni Henthorn in Rocky Mountain National Park. Henthorn died after falling from a steep cliff, and her husband Harold had claimed it was an accident. Shott discovered Harold had pushed her. 

The price for that kind of autonomy is being forced to be selective when tackling crimes. With so few agents and so much territory to cover, the ISB only accepts cases they stand a good chance of solving, using what Sullivan calls the “solvability matrix.”

“We look at the level of crime,” he says. “Is it a felony? What victims are involved? Is there a suspect? Is there physical evidence?” Violent crimes often get the ISB’s full attention, though resource crimes—like the Native American grave-robbing case—can rise to the level of a top priority. The Pacific Field Office took on 49 new cases in 2018. Counting existing cases, the office worked a total of 117 incidents that year.


While there is no crime unique to national parks, there is one recurring type of case that all ISB agents have to cope with at some point: Missing persons, which often turn into cold cases.

A National Park Service Investigative Services Branch Special Agent is pictured
Locating missing persons can prove challenging for the ISB.
Courtesy of the National Park Service

According to Sullivan, 30 people have disappeared from Yosemite since 1909 without ever being found. Across the whole park system, 23 people are currently listed on the NPS website as missing. It’s an eerie statistic, and one that speaks to the vast and remote territory that makes up the landscape of the national parks.

“We deal with missing persons quite a bit,” Sullivan says. “People who have just vanished into the wilderness, there is lots of that.”

Some were last seen hiking. Others are believed to have died by suicide. Many leave a car behind, the only trace left of them.

All of Sullivan’s agents have at least one cold case assigned to them. When there’s downtime, they can pick up the thread and work on it. If tips come in from a call or the ISB’s social media presence on outlets like Twitter, the case can warm up again, but they often have to take a back seat to cases meeting the solvability matrix.

Among the most prominent of the missing is Paul Fugate, a park ranger who disappeared from Chiricahua National Monument in Arizona on January 13, 1980. After walking away from his station to hike a park trail, he was never seen again. Investigators suspected foul play was involved, but the case has yet to be resolved.

Stone hoodoos in Chiricahua National Monument
Chiricahua National Monument
PatrickPoendl/iStock via Getty Images

Sometimes a body appears with no context. “Jane Doe,” who was found in Yosemite’s Summit Meadow in 1983, was a young woman believed to be the victim of serial killer Henry Lee Lucas, though that’s never been proven. (Lucas, prone to falsely confessing to unsolved murders, died in 2001.)

Not all such cases come to unhappy ends. In January 2020, visitor Martin Edward O’Connor was located at Grand Canyon National Park after being missing for nearly two weeks.

Sullivan tries to resolve cases like this one as best he can. With a small staff and the same number of hours in the day as anyone else, it can be difficult. The ISB is often unheralded, with Sullivan hearing a repeated joke about agents “investigating pinecones.” That could change if the ABC television network moves forward with a proposed series about the agency, set to be produced by Kevin Costner.

Regardless, agents will still be policing a serious expanse of public land. “Yosemite gets 5 million visitors a year,” he says. “That’s 15,000 to 20,000 people a day. We have the same problems as any population the same size. We’re here to deal with it.”

10 of the Most Popular Portable Bluetooth Speakers on Amazon


As convenient as smartphones and tablets are, they don’t necessarily offer the best sound quality. But a well-built portable speaker can fill that need. And whether you’re looking for a speaker to use in the shower or a device to take on a long camping trip, these bestselling models from Amazon have you covered.

1. OontZ Angle 3 Bluetooth Portable Speaker; $26-$30 (4.4 stars)

Oontz portable bluetooth speaker
Cambridge Soundworks/Amazon

Of the 57,000-plus reviews that users have left for this speaker on Amazon, 72 percent of them are five stars. So it should come as no surprise that this is currently the best-selling portable Bluetooth speaker on the site. It comes in eight different colors and can play for up to 14 hours straight after a full charge. Plus, it’s splash proof, making it a perfect speaker for the shower, beach, or pool.

Buy it: Amazon

2. JBL Charge 3 Waterproof Portable Bluetooth Speaker; $110 (4.6 stars)

JBL portable bluetooth speaker

This nifty speaker can connect with up to three devices at one time, so you and your friends can take turns sharing your favorite music. Its built-in battery can play music for up to 20 hours, and it can even charge smartphones and tablets via USB.

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3. Anker Soundcore Bluetooth Speaker; $25-$28 (4.6 stars)

Anker portable bluetooth speaker

This speaker boasts 24-hour battery life and a strong Bluetooth connection within a 66-foot radius. It also comes with a built-in microphone so you can easily take calls over speakerphone.

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4. Bose SoundLink Color Bluetooth Speaker; $129 (4.4 stars)

Bose portable bluetooth speaker

Bose is well-known for building user-friendly products that offer excellent sound quality. This portable speaker lets you connect to the Bose app, which makes it easier to switch between devices and personalize your settings. It’s also water-resistant, making it durable enough to handle a day at the pool or beach.

Buy it: Amazon

5. DOSS Soundbox Touch Portable Wireless Bluetooth Speaker; $28-$33 (4.4 stars)

DOSS portable bluetooth speaker

This portable speaker features an elegant system of touch controls that lets you easily switch between three methods of playing audio—Bluetooth, Micro SD, or auxiliary input. It can play for up to 20 hours after a full charge.

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6. Altec Lansing Mini Wireless Bluetooth Speaker; $15-$20 (4.3 stars)

Altec Lansing portable bluetooth speaker
Altec Lansing/Amazon

This lightweight speaker is built for the outdoors. With its certified IP67 rating—meaning that it’s fully waterproof, shockproof, and dust proof—it’s durable enough to withstand harsh environments. Plus, it comes with a carabiner that can attach to a backpack or belt loop.

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7. Tribit XSound Go Bluetooth Speaker; $33-$38 (4.6 stars)

Tribit portable bluetooth speaker

Tribit’s portable Bluetooth speaker weighs less than a pound and is fully waterproof and resistant to scratches and drops. It also comes with a tear-resistant strap for easy transportation, and the rechargeable battery can handle up to 24 hours of continuous use after a full charge. In 2020, it was Wirecutter's pick as the best budget portable Bluetooth speaker on the market.

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8. VicTsing SoundHot C6 Portable Bluetooth Speaker; $18 (4.3 stars)

VicTsing portable bluetooth speaker

The SoundHot portable Bluetooth speaker is designed for convenience wherever you go. It comes with a detachable suction cup and a carabiner so you can keep it secure while you’re showering, kayaking, or hiking, to name just a few.

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9. AOMAIS Sport II Portable Wireless Bluetooth Speaker; $30 (4.4 stars)

AOMAIS portable bluetooth speaker

This portable speaker is certified to handle deep waters and harsh weather, making it perfect for your next big adventure. It can play for up to 15 hours on a full charge and offers a stable Bluetooth connection within a 100-foot radius.

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10. XLEADER SoundAngel Touch Bluetooth Speaker; $19-$23 (4.4 stars)

XLeader portable bluetooth speaker

This stylish device is available in black, silver, gold, and rose gold. Plus, it’s equipped with Bluetooth 5.0, a more powerful technology that can pair with devices up to 800 feet away. The SoundAngel speaker itself isn’t water-resistant, but it comes with a waterproof case for protection in less-than-ideal conditions.

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This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

Cracking Open the History of Unsolved Mysteries

Robert Stack hosts the original Unsolved Mysteries.
Robert Stack hosts the original Unsolved Mysteries.

With his steely glare and trademark trench coat, Robert Stack took viewers on a journey through tales of true crime, alien abductions, amnesia, and lost loves. It was Unsolved Mysteries, and on this week’s episode of "Throwback," host Erin McCarthy is taking us down some dark alleys to discover the origin of this classic 1990s series that’s being rebooted on Netflix. Join us.

Be sure to head here and subscribe so you don't miss an episode of "Throwback," where we explore the fascinating stories behind some of the greatest toys and trends from your childhood.