Substantially incomplete response.
Jury nullification originated in England, the 'founder' of our Common Law. Juries did not want children stealing bread to eat (read:to not starve to death) to be convicted of a capital crime and be executed.
Eventually that society (and ours) learned we don't execute children for theft, then extended to adults; we don't cut off hands or arms for theft either.
It's (also) a check and balance where a prosecutor can 'get a jury to indict a ham sandwich'. /UNRELATED RANT
so i dont want to post as AC so wrongly programmed Slashdot doesnt retain the RSS link after I (re-) register. Can go to main Slashdot but that sets off my No-Script. had to kill page then click on RSS again (not as easy since all marked as Read) and fortunately I stayed login.
FAIL, Slashdot programmers/ sw. /end unrelated rant