Answer

Good question. Intuitively, it seems to me that yes. One could engage in pilpul here about the laws of damages and murder in a case where the injured person dies only after some time has passed (as in the law of "a day or two")—whether tort liability or criminal liability is imposed on the assailant. But nowadays, since we have medical tools to determine responsibility, in my opinion these laws have no significance, and the time gap is not important.
Similarly, one could discuss a pursuer who injured the pursued, and now one no longer has permission to kill him. But one may take an organ from him (even if his breathing depends on it) and transplant it into the pursued in order to save his life. Intuitively, it seems that one may and should do that as well.
And here too one can argue back and forth: if we understand that killing the pursuer is done in order to save the pursued, then seemingly this is straightforward. But Rashi in Sanhedrin implies that this is done in order to save the pursuer from committing a transgression (and this requires further examination in the case of a minor pursuer), and then there is room for the argument that one does not commit a transgression in order to save someone from an act that has already been done. Similar to what Tosafot wrote in Babylonian Talmud, Sabbath 4a, regarding one who stuck bread to the oven wall: there is no permission to remove the bread in order to save him from the prohibition of baking on the Sabbath, because the sticking has already been done, and the rescue only prevents it from becoming a transgression. One tells a person to sin only in order to save from a transgression that has not yet been committed. But of course there is room to distinguish that case from the present one.