Is expiation obligatory for someone who caused the death of their companion in a car accident resulting from colliding with a large rock that completely disabled the car, and what are the consequences if they are unable to fast for two consecutive months?

The determining factor for a driver bearing the financial compensation (Diyya) and expiation (Kaffara) in traffic accidents is the extent of their responsibility for the accident. Their guarantee for what was damaged, whether lives or property, is based on their negligence, dereliction, and the degree of their error. The determination of this is referred to the report of the competent authorities, such as the traffic police. If you are not responsible, there is no expiation. If you are responsible, then expiation is incumbent upon you. If you are temporarily unable to fast, then wait until you are able. If the inability is permanent, the more cautious approach is to feed sixty needy persons.