Sometime before dawn on March 27, 2016, a 25-year-old American named Colin Madsen walked out of a cabin in eastern Siberia. His three friends, with whom he’d planned to hike in the nearby Sayan Mountains just hours later, were asleep in the house, oblivious to his exit.

Eight days later, his body was found by a search party outside of Arshan, the tourist town 200 kilometers southwest of Irkutsk where the group had been staying.

It remains unclear precisely how Madsen ended up dead beneath a large tree, his body resting on its back on wilted spring vegetation with an extended left arm and clenched fists.

Investigators in the Siberian region of Buryatia, where Madsen’s body was discovered, opened a murder investigation, a standard procedure in missing-persons cases.

They eventually concluded he’d been taking drugs -- an illegal cannabinoid -- with his friends shortly before he vanished sometime between 2 a.m. and 5 a.m. and that he “froze to death” after wandering out of the cabin dressed only in light clothing.

But Madsen’s family was almost immediately suspicious of that conclusion.

Madsen's mother, Dana Calcutt, had traveled to Arshan shortly after her son vanished to participate in the search. On April 6, two days after his body was discovered, she wrote on Facebook that she believed authorities were “trying to cover up the ineptitude that occurred here before we came and the pressure to find him was accelerated.”

Fifteen months later, Calcutt believes there is even greater reason to suspect foul play in her son’s death.

I think something happened, and they didn’t want it to appear that an American had been murdered in Russia.”

An analysis she commissioned from U.S.-based forensic scientists who examined a range of case materials has concluded that there is “strong” evidence that her son “was physically abused and died in the process.”

“I think something happened, and they didn’t want it to appear that an American had been murdered in Russia,” Calcutt told RFE/RL.

‘A Trusting Person’

Madsen, who arrived in Irkutsk from Missouri in 2013, was an avid and experienced hiker who fell in love with the physical beauty of the region. According to those who knew him, he enjoyed his studies at the state linguistics university in Irkutsk, a major industrial city on the edge of the world’s largest and deepest freshwater body, Lake Baikal.

Madsen’s love of the outdoors had led him to volunteer with environmental groups in the area, Calcutt said.

He helped build hiking trails around Lake Baikal for a Russian nonprofit called The Great Baikal Trail and volunteered with local activists from Greenpeace, participating in several protests. Months before his death, Calcutt said, he had received a warning letter from local authorities about his participation in the protests.

The American student and his Russian friends frequently ventured out into the Siberian wilderness, occasionally landing in challenging situations, such as difficult routes after dark with no obvious landmarks in sight. But Madsen was conscientious about preparation and knew how to stay safe in the mountains and forests, according to his family and friends.

On the day he disappeared, he and his three hiking mates -- two Russians and another American -- were set to head out on a 3.5-kilometer hike they had mapped out. They turned the lights out at 2 a.m., planning to wake three hours later and set off at 7 a.m.

But when the others awoke at 5 a.m., Madsen was gone. His backpack and other items had been left behind.

Arshan is a popular weekend destination for people looking to spend time outdoors along the banks of the Kyngarga River. One member of the group told RFE/RL it is unlikely that Madsen slipped out into the night and subsequently went to party with some other night owls in the area.

“But he was a trusting person,” the friend said on condition of anonymity, citing concerns about potential retribution from authorities.

“It’s possible he may have been hoodwinked” and “jumped,” the friend added.

“The injuries on the body and the tearing of his clothing do indicate that the victim was in some sort of fight.”

When Madsen didn’t show up by 7 a.m., his friends began to panic. They scoured the village for any sign of him and then went to the local police precinct house, which was closed. In the evening, they finally managed to contact police, and officials from the Investigative Committee -- the Russian analogue of the U.S. Federal Bureau of Investigation -- soon arrived in Arshan.

Madsen’s friends say investigators first pressured them to confess to killing their friend in a drug-and-booze-fueled fight and hiding the body. They became irritated after learning that the hikers were teetotalers, the member of the group told RFE/RL.

If there was ever any serious consideration by authorities that Madsen’s friends were involved in his death, it went nowhere. The Buryatia regional branch of the Investigative Committee said in May 2016 that it would open a criminal case against unidentified members of the group based on alleged drug possession and use.

On April 1, the day she arrived in the area, Calcutt and a translator provided by Madsen’s university met with a police officer in a town near Arshan. The officer, she said, yelled and spat, insisting that Madsen was gay -- which Calcutt said he wasn’t -- and insinuated that there had been some sexual orgy. Then he insisted on knowing how much money Madsen had, according to Calcutt. The translator, she said, got into a yelling match with the officer.

The other American with Madsen at the time, a man identified as Lucas Fagre, did not respond to requests from RFE/RL for comment. But last year, after Madsen went missing, he told a Missouri television station that the circumstances surrounding the disappearance were strange.

"On the one hand, it seems kind of like him, for him to just leave like that. But I don’t know. Just a lot of things are off," Fagre said.

Asked about Madsen’s case, the U.S. State Department issued a brief statement.

“We have closely monitored local authorities’ investigation into the cause of his death. We refer you to the Russian authorities on their investigation,” an official told RFE/RL in an e-mail, speaking on customary condition of anonymity. “We have no power to conduct investigations on Russian territory.”

‘Flat On His Back’

It took a search party that involved volunteers eight days to find Madsen’s body about 1.5 kilometers outside Arshan. Someone involved in the search appears to have snapped a photograph of his corpse that was leaked to the sensationalistic Russian news site Life.ru.

To Calcutt, who had arrived in Arshan four days after her son went missing, the photo helped highlight what she considered inconsistencies in details that had been emerging from the investigation -- including that he was wearing a T-shirt and succumbed to the cold. In the photograph, Madsen is wearing a long-sleeve blue shirt, which Calcutt called a “thermal shirt.”

“If anyone knows Colin, he had an incredible tolerance to cool weather,” Calcutt wrote.

She added that he was “not huddled or covered with leaves but flat on his back in grass with his sleeves pushed up, his boots unlaced, no socks on, his eyes and mouth open. He was not in snow but on the grass under a tree.”

“He would have never walked to a place in the pitch dark with his shoes unlaced, no socks, and when he was leaving for a climb in just a few hours that he was so excited about,” Calcutt wrote in the April 6, 2016, post.

She suggested her son may have left the cabin to use an outdoor toilet and that “if Colin did any drugs [which we don't know] he would have smoked marijuana and that was hours before this event occurred. There was no alcohol involved.”

Investigators found Madsen's wallet, containing cash, and his U.S. passport at the scene, suggesting he was not the victim of a robbery.

‘Suspicious Circumstances’

In July 2016, some three months after her son’s death, Calcutt returned to the Arshan district and obtained the Russian autopsy and toxicology reports, as well as crime-scene photos.

A Russian drug screening included in investigative materials seen by RFE/RL came back negative in tests of his hair, blood, and nails. But it states that Madsen’s urine test revealed the main urinary metabolite of cannabis products, with a concentration of 16.6 nanograms per milliliter.

Other “suspicious circumstances” include “injuries all over [Madsen’s] body" that are “not explained by running through the woods” and “injuries on his hands and wrists” that “indicate that the victim had been held.”

For context, the World Anti-Doping Agency (WADA) threshold for that urinary metabolite -- known as 11-nor-9-carboxy-delta-9-tetrahydrocannabinol -- is 150 nanograms per milliliter. Anything below that and WADA-accredited laboratories are not required to report an “adverse analytical finding.”

Atholl Johnston, a toxicology expert at Queen Mary University of London, told RFE/RL that the concentration that was found in Madsen’s urine, according to the Russian investigation, suggests he could have smoked or ingested cannabis up to several days prior to his disappearance.

But he said it was “definitely not” a large amount. The traces could have remained in his urine for several days if his body were outside in cool temperatures, Johnston added.

A laboratory at Washington University in St. Louis also conducted a toxicology test on Madsen’s liver. It came back negative for a range of drugs, including cannabis, according to a copy of the report obtained by RFE/RL.

Johnston said, however, that if the Russian investigation is to be believed, the negative test could be a result of how the samples were handled -- or that any concentration found was considered too small to report.

A television network in Buryatia quoted a regional Investigative Committee official as saying on the day that Madsen's body was found that the dead student and his “group were using drugs over the course of the day.”

But authorities conducted a drug screening on at least one other member of the group that Madsen had been staying with and planned to hike with. That test, which was conducted three days after Madsen’s body was found and seen by RFE/RL, came back negative for controlled substances.

Calcutt and her husband, University of Missouri professor Mick Calcutt, proceeded to commission an independent examination of their son’s death.

They reached out to the Colorado-based Independent Forensic Services, which has worked on several high-profile U.S. criminal cases and also generated some local controversy over the firm’s credentials.

The firm’s Dutch-born forensic scientists examined a range of materials related to the case, according to a copy of the report seen by RFE/RL. These materials included video and documents from the Russian autopsy, the Russian toxicology report, crime-scene and U.S. autopsy photos, and the U.S. autopsy report.

The experts, Richard Eikelenboom and Selma Eikelenboom-Schieveld, observed that the reported stiffness of Madsen’s body at the crime scene -- such as his seemingly clenched fists -- suggested that he may have been alive for several days after his disappearance.

“After eight days, one would expect this to be absent,” they wrote.

They added that based on weather conditions and temperatures, “it is very unlikely the victim was lying in the forest for eight days” and that one would expect greater damage to his body from animals had it been at the site for that period of time.

“It is unlikely that the victim died on the location where he was found,” the analysis states.

Other “suspicious circumstances” include “injuries all over [Madsen’s] body" that are “not explained by running through the woods” and “injuries on his hands and wrists” that “indicate that the victim had been held.”

“The injuries on the body and the tearing of his clothing do indicate that the victim was in some sort of fight,” Eikelenboom and Eikelenboom-Schieveld conclude.

The regional Investigative Committee branch in Buryatia did not respond to an RFE/RL request for comment on Calcutt’s criticism of the investigation.

Calcutt told RFE/RL that she is drafting a letter to send to the White House’s Russia point person, Fiona Hill, seeking assistance in the matter and that she plans to send the same letter to U.S. President Donald Trump.

Asked whether she believes her son may have been still alive when she arrived in Russia to join the search, Calcutt said: “I don't know for certain when Colin was killed, but I do fear it was while I was in Arshan.”