I’m sure many of us who teach writing have seen this error, but it never ceases to amuse me.
My student was explaining why the judge didn’t send killer-dad to prison: he was not going to be killing anyone else anyway; he killed his son out of love (so went the claim), and so he wasn’t really a killer.
I would certainly agree that a cereal killer probably doesn’t belong in jail, whether he went wild in the supermarket aisles and slaughtered a few boxes of Quaker Oats and Rice Krispies, or ran amok in a field of wheat and chopped down some stalks. Impose a fine, sure, or community service. That should be enough to teach him a lesson not to assault pacifists, chatty elves, or amber waves of grain.
Serial killers are far, far worse. They take lives without pity and terrorize whole communities. What my student meant is right: the father in the case was not a serial killer, or at least showed no signs of becoming one.
What she wrote is probably also true. But he wasn’t on trial for murdering Müesli.