Speed was the probable cause of a fatal accident in the early hours of March 16 on State Road 76.    New Mexico State Police Officer Jarod Escareno was dispatched to the accident. He arrived at 5:18 a.m. and found John Dickason, 43, Truchas propped up in a pine tree quite a distance from the road.    Escarenoâs lapel video indicates volunteer firefighters came upon the accident after they had fought a fire north of Truchas at about 3 a.m.    Escareno determined from the skid marks and pavement gouges that Dickason was traveling north in his Ford pickup and while negotiating a curve at a high rate of speed left the road.