Investigators are hoping that video footage inadvertently captured by a German eyewitness will shed light on Michael Schumacher’s skiing accident last week.

The Formula One legend remains in a coma and in critical condition following the accident in the French Alps.

But now, a 35 year old German eyewitness says he caught the accident on his smartphone by chance while recording his girlfriend who was also skiing in the same area at the time.

Investigators are focusing on Schumacher’s speed at the time of the fall when Schumacher slammed his head on a rock on a small off-piste section of the Meribel ski resort. They are also looking into footage from a small GoPro camera which Schumacher had mounted on his helmet at the time of the fall. His family is said to have handed the camera over to investigators but it is unknown yet whether any of the footage will be usable or whether the camera was too badly damaged in the fall. Schumacher’s helmet is said to have split in two on impact.

In a press conference last week, doctors who treated Schumacher said he had been skiing at “great speed” when he fell.

However, according to news magazine Der Spiegel who spoke to the witness, Schumacher is seen descending an unmarked run between two groomed pistes before falling, and the seven-time world champion was descending the slope at a “leisurely” pace – “a maximum speed of 20 kilometres an hour”.

This would corroborate claims by Schumacher’s spokesperson Sabine Kehm, who insisted that he could not have been going fast “because it appears he helped a friend who had just fallen”.

Prosecutors are also working on determining responsibility for the accident. They’re looking into whether the limits of the ski runs were properly marked; whether the rock in question may have been close enough to the piste to require some sort of signage or protection; and whether the safety releases on Schumacher’s skis had operated properly.

Police have also obtained eyewitness testimony from Schumacher’s 14-year-old son Mick as well as a friend, who were skiing with him at the time.

Kehm has said that Schumacher remains in a “critical but stable condition” after undergoing two surgeries to release pressure and bleeding on the brain.

Schumacher’s wife Corinna and his two teenaged children have remained by his bedside throughout.

His old rival, and good friend, Mika Hakkinen wrote to Schumacher according to the Bild am Sonntag newspaper saying, “Your accident is now just another challenge. You have to fight hard again, just like we both used to do on the track. Do me a favour: just this once don’t try to beat the clock. You don’t have to post your best time in this race. You have to take all the time you need.”