Reply To: The Ins & Outs Of Nezek

In short:

b’rshus is chayav unless someone else is poshea; then b’rshus is o’nes.

When both the mazik and nizik are b’rshus its like both are poshea and the mazik is chayav if he is mazik him with a mayseh.

But if he is mazik him in a bor way, then by both b’rshus the mazik is patur, since if both were poshea the ba’al habor is patur.

So it turns out that bor b’rshus is chayav only if the other is o’nes gamur. If the nizik is poshea every bor is patur, but if the nizik is b’rshus then a regular bor is chayav but a bor b’rshus is patur.

A different tosphos argues on this. This approach holds that two b’rshus shows favor to the nizik, allowing him the o’nes, and the mazik is always chayav by shneyhem b’rshus. This tosphos holds that the reason the guy in front stopping needs to be poshea (to be michayev him as a bor) is only because if he wasn’t poshea, then the guy in back would have been poshea and then the first guy b’rshus would have been patur. The R”I can’t hold this, however, because he holds that the second guy is b’rshus about not watching where he is going regardless of what the first guy does.