Lindsay Jacobellis snatched defeat from the jaws of victory in a manner of which Devon Loch would have been proud in the women's snowboard cross final at Bardonecchia.

Like the Queen Mother's horse, which famously belly-flopped before the finish line in the 1956 Grand National, Jacobellis appeared certain of victory as she led the field by almost 100 yards.

But Jacobellis attempted an ambitious 'hot dog grab' on the last big jump and fell upon landing, allowing Switzerland's Tania Frieden, who had given up the chase, to sail home for gold.

Jacobellis, who nearly slid over the line on her back, recovered to claim silver, said: "I was really excited and everything seemed to be going well then I landed badly.

"I got a bit frustrated because I have worked so much, but an Olympic silver medal is still an Olympic silver medal."

American coach Peter Foley, who fell to the ground in despair when Jacobellis failed in her attempt at a grandstand finish, said: "I don't think she was showing off - she just cut an edge.

"She was so far in front it's got to be hard. I was staring at the screen screaming, "keep racing, keep racing". I don't think anyone has it until you cross the line."

Britain's Zoe Gillings, who finished 15th, said such an occurrence was nothing new in a sport in which four finalists tear down the narrow course at the same time.

"I think she was trying to show off but she didn't land her trick," said Gillings. "But that's snowboard cross."

Russian biathlete Olga Pyleva has been stripped of her Olympic silver medal after testing positive for the banned stimulant carphedon.

Pyleva - who finished second in Monday's 15km individual - is the first athlete to be expelled from the Turin Games due to a doping offence.

The 30-year-old's silver has now gone to third-place finisher Martina Glagow of Germany, with Russian Albina Akhatova upgraded to bronze and Pyleva must now face Italian magistrates.

Canadian skeleton star Duff Gibson announced his retirement after becoming the oldest individual gold medallist in Winter Olympic history.

Gibson said: "I think it is a well-known fact that I am not the youngest guy in the sport, and the important thing for me was to go out on top.

"Winning is exactly how I dreamt it would feel. I vividly remember when I was 10 watching the Montreal Games - and I wanted to be a part of it."