No one is going to be able to give you much of a realistic answer without some strong specifics, like:

. . . how many miles on the car.

. . . had the ball joints ever been replaced.

. . . how fast was your son going when he ran off the shoulder.

. . . how much of a shoulder did he run off of.

These are only a small, small percentage of the number of questions that need to be asked.

You say that you son hit ran off a shoulder, causing the ball joint to break, causing your son to loose control. I would assert that your son lost control before he hit the shoulder.

I am bothered by the tenor of your posting. I hate when I read posts where someone blames someone (or a car manufacturer) for complete responsibility for a problem when it is evident that they (your son) contributed to this situation.