While installing a new wheel bearing the
mechanic broke the steering knuckle who is
You mean liable? Believe me I have broke things in my years as a Tech and have always footed the cost of the part I broke, but by being honest about it some of the customers would kick in half of the part cost and I would eat the labor cause I broke it. That's why I check everything over before I start a job just to make sure everything is in good condition. So to answer your question the shop is unless he can prove it was already deteriorated and that will be obvious.