Good question. Liability will depend on the facts of the accident. I have not researched this issue for some time, but my recollection is the supervising driver is not considered at fault, even if the driver is. Make sure to report this matter to the insurance carrier for the registered owner also.
The law varies in different states. If every supervising driver was responsible when a driver with a learners permit had an accident, there would be no supervising drivers and nobody would ever learn to drive. My opinion? The supervising driver is not responsible. Contact a personal injury attorney in your area immediately.
This response is given solely as a general response to the question and does not create an attorney / client relationship between the questioner and responder.
Liability goes first to the driver and registered owner of the vehicle. Thankfully, he has insurance. If the supervising driver was negligent in some manner, and there was not enough insurance to go around, then he or his firm, he is a commercial supervisor, could also find himself a target of the lawsuit, specially if he was negligent in any way whatsoever. Specially, if he knew the driver was not ready to go to the highway. Best of luck.
This answer is provided by Manuel A. Juarez, Esq., El Abogado de Accidentes de Autos de California: 510-206-4492. El Abogado de Accidentes de Autos provides answers of a general context. These answers are not intended to form an attorney client relationship. El abogado de Accidentes de Autos y Lesiones Personales practices in Antioch, Berkeley, Concord, Oakland, Hayward, Martinez, Newark, Richmond, San Francisco and San Rafael. El abogado de accidentes y lesiones is licensed only in California. This information is good only in California and it is not to be taken as legal advice on car accidents, personal injury, divorce, bankruptcy or in any other type of situation. Esta respuesta es del Abogado de Accidentes de Autos y Lesiones Personales de Acidentes de carros, Manuel A. Juárez, 510-206-4492. Abogado Hispano de Accidentes, Divorcios, Abogado Latino de Accidentes, y Abogado de Acidentes de Oakland, Hayward, San Francisco, y California. Estas respuesta son solo para información general y no consisten en consejo legal sobre divorcios, mantención de esposas, mantención de hijos o bancarrotas. Las respuestas son comentarios legales que no forman una relación de abogado y cliente. Manuel Juarez, Esq., esta licenciado solo en el Estado de California.