[annie123 (OP)]

Is there any scientific explanation as to why some bodies - usually saints - show no signs of decomposition when exhumed after many years? (eg St Cuthbert)

[evan_au]

Peruvian mummies were left in cold, dry caves, causing the bodies to dry out, to the point where bacteria could not survive.

Egyptian mummies were dried out, perishable organs removed and treated with chemicals that discouraged bacterial growth.

Actual brain tissue has been found in bodies buried in peat, where the lack of oxygen discourages the common bacteria that would digest most things.

[annie123 (OP)]

Yes, but I am thinking of bodies which have been put into coffins as is- usually just wood- and into ordinary graveyards and then dug up again later. I was reminded of this when i was watching a doc about St. Cuthbert. There have been other examples not to do with peat or embalming etc.

He died on Farne Island on March 20th 687 AD. He was buried at Lindisfarne.
When the monks moved his body to a new tomb eleven years later it was found to be incorrupt.
An impressive Cathedral was built at Durham to hold the shrine of St Cuthbert. The coffin was placed in it on 1104 AD, the body was found still incorrupt at this stage. September 4th became another feast day, The Translation of Saint Cuthbert. The shrine became a major place of Pilgrimage. St Cuthbert’s banner was carried by English troops in their wars against the Scots.
At the time of the Reformation, the shrine, which contain many valuable jewels was robbed and St Cuthbert’s book now called the Lindisfarne Gospels stolen. Cuthbert’s coffin was once more opened and the corpse was found still uncorrupted.

[Bored chemist]

Being dried out is the most plausible answer. Possibly salted if he was originally buried on Lindisfarne.
You might also want to consider just how honest the monks could have been about it: worship implies that you think he's miraculous so...

[syhprum]

Good money was made from pilgrims visiting ancient shrines so its quite likely that some doctoring of relics took place.
Even today plenty of statues of the "blessed virgin" weep tears of blood and serious researchers are kept away from bits of the true cross and the Turin shroud

[exothermic]

Is there any scientific explanation as to why some bodies - usually saints - show no signs of decomposition when exhumed after many years? (eg St Cuthbert)

The very fact that they were saints means that special care was taken to preserve them.

Dig up the guy next to the saint, and I'd be willing to bet there'd be nothing but bones.

"The Catholic belief of “incorruptibility” holds that if a body does not decay after death, the person is holy. It takes two miracles to become a saint; the Church once allowed a perfect corpse to count as one."

http://nypost.com/2014/03/22/making-of-a-saint-the-vaticans-quest-to-preserve-its-leaders/

[RD]

... some doctoring of relics took place...

I did read than Lenin is given a formaldehyde-bath every couple of years ...
http://www.theatlantic.com/international/archive/2016/04/lenins-body/478050/

Also in Moscow he'll be at fridge-temperature, (4^oC), or lower for most of the year.