It appears that juries have been around a lot longer (circa Magna Carta, 1215?) than the United States, and from the very beginning of juries, there was the realization that a group of common people would be in a better position to judge the accused than entrusting a single individual to make such a decision.
Jury Nullification, to put it bluntly, is a way for the jury to say: "We, the jury, disagree with your (i.e. overzealous prosecutor, rogue judge, etc.) legalistic (mis)interpretation of the law, and as such, release the accused of the charges against him".
If judges can overrule the jury's ability to do the above, we are back in the dark days of individuals (e.g. Kings, Emperors, Saddam Hussein, etc.) making unruly decisions over an individual's fate.
Jury Nullification is not the ability of a judge to "nullify" the jury.
The original shoplifting case 2 threads back is an example of a very harsh (possible) sentence for the accused, if she decides to exercise her right to a decision by jury.
It would seem that such harsh punishments were basically designed to coerce the accused to "admit" to offences they might not have committed, to make a prosecutor look good or to reduce the workload on the legal system.
A better and more reasonable solution would be to make the accused pay for maybe 3(?) times the cost of the item and additional fees (court/jury time, loss prevention dept fees, etc.) if found guilty after a trial by jury (which in itself should be a sufficient deterrent for a guilty party to unjustly try to burden the legal system), and not the very harsh and permanent punishment described. Since this wasn't an option presented to the accused, Jury Nullification would be appropriate here, IMO.
I sympathize with the predicament of the accused in that "shoplifting" case.
