The mystery surrounding the violent murder of a Stone Age man in the Swiss Alps 5,000 years ago is to be uncovered by scientists.

The Iceman Murder Mystery documentary examines Otzi, whose body was found preserved in an Alpine glacier in 1991.

For 20 years, researchers have tried to ascertain how Otzi died. X-rays of his body gave little indication of his death so scientists took the decision to defrost his corpse.

The team has nine hours to perform an autopsy on the mummified body, providing them with DNA evidence of his last meal and indications of how he died.

They find that Otzi was living at a time of change in the Neolithic Age. He had complex weapons with him when he was found, as well as a wooden back pack and shoes, suggesting he had planned to walk into the mountains.

Iceman autopsy
Otzi was shot in the back with an arrow (Channel 4)

However, while conducting their research, they find he had been shot in the back with an arrow. The shaft of the arrow had been removed, adding further mystery to his death.

Otzi also had a wound on his hand, which some think indicates he died in hand-to-hand combat.

This theory is soon debunked though. None of his possessions, including a copper axe, which would have been an advanced weapon for the time, were taken from him - leaving scientists wondering if his murderer wanted to avoid identification.

The narrator explains: "That axe was so advanced some believe it marks Otzi as a man of great importance in his community. Stone carvings found in the valley below where he died prominently feature the exact same kind of axe, suggesting that the weapon had great symbolic power."

Alpine archaeologist Patrick Hunt adds: "If you took his axe, you'd be identified; if you left your arrow shaft, you could be identified. So, to leave the axe and take the arrow says that someone is exercising great caution.

Iceman autopsy
Otzi was Sardinian and suffered from Lymes disease (Channel 4)

"They're thinking this through. Possibly, they don't want to be identified as Otzi's killer."

As the mystery unfolds, the team finds out more about Otzi. He had brown eyes, was around 5ft 2 and that his closest genetic match living today would be from Sardinia.

He was also suffering from Lymes disease, demonstrated by the swelling found in one of his knees.

As the researchers analyse the contents of his stomach, they find he ate a large meal before his death and was hit on the head with a blunt object, leading them to conclude he was murdered by someone he knew.

Iceman Murder Mystery is on More4 at 9pm tonight (Wednesday).