Karl Childers is a mentally challenged, limping murderer with terrible hair. You know, your typical Hollywood protagonist.
Okay, he's far from typical, but he does have one character trait that movies love: a heart of gold. Yep, he's a mentally challenged, limping murderer with terrible hair and a heart of gold.
We can hear you asking, "How can someone who murdered two people have a heart of gold, mmhmm?" And we hear you asking that in your best Sling Blade voice, and sorry to tell you, but your accent needs work. Anyway, when you think about it, the human heart is made of many different elements—muscle, blood, iron, oxygen. But heart of gold is made of one thing: gold. It's simple.
And Karl, raised in a shack and fed a steady diet of Bible scriptures, is simple. He's like a child. In fact, you can't even spell his last name, Childers, without "child," and that's a sign. Karl believes in absolute morality, in Biblical justice. Do something bad, like have an affair, and you will be struck down.
But there's something else in the Bible: "Thou shalt not kill." That little commandment comes before the adultery one and the one about coveting your neighbor's wife, your neighbor's house, and your neighbor's Tesla. Looks like Karl broke one commandment in order to punish someone for breaking another. So Karl, as a child, accepted his punishment when he was committed to a mental hospital.
KARL: I reckon the reason I'm in here is 'cause I killed somebody. Mmhmm.
We reckon that Karl is someone who doles out punishment, but who also takes the punishment he is given. He does it again at the end of the film, committing a crime with the full knowledge that he'll do the time for it. Does that make him hypocritical? Or does it all make sense within Karl's narrow view of the world?
A Whole New World
Everything we've talked about so far takes place before the movie begins. The movie actually begins when Karl is released from the mental hospital back into the new world. For Karl, it's like being a deaf man who not only can suddenly hear, but is also dropped into a Nickelback concert for his first auditory experience. It's overwhelming, out of control, and a little scary, but maybe—just maybe—he kinda likes it.
He likes it a little because even in terrible places like Nickelback, you can find good people. And Karl is lucky enough to find Frank, a young boy who is both a friend and a younger brother to him. Growing up in a literal hole behind his parents' house, Karl only had to take care of himself. But with Frank, Karl explores what it's like to be a big brother and caretaker.
Karl takes "big brother" as his primary role, and he sees Frank's mom's boyfriend Doyle as his nemesis. Doyle is emotionally abusive to Frank and threatens to be physically abusive. Karl stands up to Doyle, literally coming between him and Frank.
KARL: Mister, don't you never lay another hand on that boy. You understand me?
You can see where this is going from the beginning of the movie, and you'll probably be counting down the minutes until Doyle's inevitable demise. But Sling Blade isn't a movie about shocking plot twists. Karl Childers is a protagonist who embodies WYSIWYG: What You See is What You Get. When Karl kills Doyle, it surprises only Doyle, in the moments before his death, because Doyle never tried to understand who Karl was below the surface.
Why'd You Have to Go and Make Things So Complicated?
It might be surprising that Karl goes ahead and kills Doyle, especially after we've seen Frank get Karl to consider his past crime and question whether or not committing was right thing to do.
FRANK: Were they bad people?
KARL: I thought they was.
The past tense here implies that Karl now thinks they might not have been bad people. As someone who is finally growing up, Karl sees that the world is a complicated place: it's not black and white. Do you think he would commit the same crime if he knew then what he knows now?
It's difficult to say. Karl can fix a lawnmower blindfolded, but navigating the real world is complicated for him. He is torn between his present reality as Frank's guardian and his past actions as a self-righteous murderer. He ends up reconciling these two identities by becoming both. He thinks he is doing Frank a service by murdering Doyle. But has he done more harm than good?