THEY claim to have seen UFOs, investigated Bigfoot sightings and hunted spirits said to take on animal shapes to haunt humans.
Now the pair, known as the Native American X-Files, are heading to Scotland to share their experiences.
It was while driving across the Arizona plains that Jonathan Dover says he witnessed his first UFO.
Since then Jonathan and fellow federal ranger Stan Milford have spent years investigating the unexplained in south-west America.
The pair will be guests of honour at the first Scottish Paranormal Festival in Stirling over Halloween weekend.
The Visit Scotland-backed event, which features talks, movies and interactive events, has been set up by Scottish film-maker Peter Broughan, who made the Liam Neeson blockbuster Rob Roy.
The event is also supported by Ghostbusters star Dan Aykroyd who sent the producer several cases of his exclusive Crystal Head vodka.
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Broughan met the rangers at a UFO convention two years ago and was determined to bring them to Scotland to share their stories.
Over the past 30 years, Jonathan and Stan have encountered dozens of cases with a supernatural element.
They are trained criminal investigators who work for the Navajo Nation government and are known for their hard-facts approach.
Recently retired Jonathan, 57, said: “My first experience was in 1984 when I was on my way home in the early hours. In the moonlight I saw a large cigar-shaped craft about 200 feet off the ground with a spotlight shining down on to the tracks. It had a really heavy engine noise.
“It was just hovering there at about 15-20mph. I got out of my car 500 feet away and watched it. There was no doubt about it, it was extra terrestrial.
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“My wife was terrified, never seen her that terrified before or since.
“She was screaming at me to get back in the car and we’ve never talked about it to this day.”
Jonathan added: “We have had quite a number of cases involving UFOs, Navajo skinwalkers, Bigfoot and hauntings. We were both first assigned to look into a Bigfoot sighting near Shiprock, New Mexico.
“About 30 witnesses had reported the sighting to police who laughed and wondered how much they had drunk. So we were sent up there and for three days we collected evidence – footprints, stride distances, hair samples – and interviewed every person we could. Our verdict was that there was definitely something.
“We investigated everything, even the case of an elderly couple living in a pine forest who had heard an animal screech they could not identify.
“Our chief ranger said he didn’t want anyone belittled, he wanted everyone investigated and documented so people knew we took them seriously. There were a lot of jokes about the X-files section, yet they accounted for less than one per cent of our work. But it was all quite amazing.”
Among the most fascinating cases were skinwalkers – shapeshifters who, it is said, can morph into an animal in order to haunt a victim.
The pair have also investigated witchcraft and poisonings, a taboo subject among their people.
The pair are not true believers – they are just as happy to rule out paranormal goings on as they are to uncover them.
Jonathan said: “We use evidence, the same standards required to get somebody tried in court.
“We don’t believe but we’ve seen enough to know there is something going on that defies explanation.
“For Bigfoot, we found footprints and stride patterns greater than five feet apart and hair samples that have been analysed and categorised as ‘unknown carnivore’.
“In the UFO realm, we’ve come up with trace evidence, ground impacts and radiation readings. With witnesses, just like any criminal case, you check their backgrounds to check if they are using any kind of drugs.
“We are trained investigators who interrogate people and read them to find out if they are telling the truth. There is definitely something but we don’t have the answers.”
And he is looking forward to coming to Scotland, saying: “We’ve never been out of the States before so this is the trip of a lifetime.”
The man bringing the Navajo team here, festival organiser Peter, said their stories would delight fans of the unexplained.
He said: “I met the guys at the international UFO Congress in Phoenix, Arizona, and they struck me as being really honest, genuine and absolutely believable when they were telling you about the most unbelievable things. We became friendly and the stories they told me over dinner were mind boggling.
“They are real-life federal-level X-files investigators and can share an amazing perspective on the paranormal and Native American culture. It’s absolutely riveting.”
■ The first Scottish Paranormal Festival runs from October 30 to November 2. The Navajo Rangers will be at the Albert Hall, Stirling, 1pm, November 2, and in Kinlochard Village Hall, Loch Lomond National Park on November 3 at 7.30pm.