I don't know about French Law but many legal systems operate an Eggshell skull principle. Also known as "take your victim as you find him".
Eggshell skull - Wikipedia, the free encyclopedia
I doubt there has been a previous case involving aircraft but was able to find one involving a collision between two ships where the judges comments suggest it applies.
http://www.seatransport.org/seaview_...0Collision.pdf
The judge's comments in the The Fedra suggests that the eggshell skull rule does apply in collision cases, provided liability for the collision has been established