GRENOBLE, France - Michael Schumacher remains unconscious but "critical but stable" in hospital here as French investigators focused on a helmet-mounted camera he was wearing when his head hit a rock.Sabine Kehm, spokeswoman for the retired Formula 1 champion, denied some reports that Schumacher's family had been reluctant to hand over the GoPro, citing privacy."Michael's helmet camera was voluntarily given to the investigating authorities by the family," Kehm said. "That this was done against the wishes of the family is untrue."HELMET SPLITThe existence of the digital movie camera was revealed late on Friday (Jan 3 2013), five days after the December 29 accident in the French Alps near the Meribel ski resort.It was not known whether the camera recorded Schumacher's ski descent or whether the images were damaged during the impact which split Schumacher's helmet.Police on Friday got eye-witness testimony from Schumacher's 14-year-old son Mick, who was skiing with his father at the time, as well as a friend.Schumacher turned 45 on Friday while still in an induced coma. Fans marked the event with a silent vigil outside the hospital.The GoPro miniature camera, robust and popular among extreme sports enthusiasts, has a 170-degree wide-angle lens that takes in much of the view and can show parts of the user's body, depending on how mounted. The latest models can take 30 images per second for six hours.If there are usable images they should shed light on the circumstances of the accident on a small, seemingly innocuous, off-piste section of Meribel located between two ski slopes - one classed 'easy', the other 'intermediate'.Conflicting statements have emerged, notably about how fast Schumacher was going when he fell, all of the circumstances vital to any insurance payout - which could be considerable.