Just being a cause-in-fact of someone's injuries does not make one liable. If it did then Karen would be able to recover against a multitude of people. The following are causes-in-fact of Karen's injuries:

Jill for driving
Mike for driving with explosives
The manufacturer and seller of Jill's car
The manufacturer and seller of Mike's car
The manufacturer and seller of the explosives
Jill's parents, grandparents, great-grandparents, etc.
Mike's parents, grandparents, great-grandparents, etc.
Karen's parents, grandparents, great-grandparents, etc.
There are undoubtedly many others who caused Jill, Mike and Karen to be where they were at the time in question.
And of course
Karen herself!

Link back to assignment 6