." . . my first thought was Bonnie. Course it was silly, but we didn't know the facts, and a lot of people thought maybe, on account of her spells." (1.256).
This shows a lack of understanding of Mrs. Clutter's depression. She would probably have been more likely to hurt herself than her family. Still, people fear what they don't understand.
I was exploring the emotional background. I thought the answer might be another woman—a triangle. Well, consider: Mr. Clutter was a fairly young, very healthy man, but his wife, she was a semi-invalid, she slept in a separate room […] (2.18)
You'd call this a "crime of passion." Agent Nye hates to suggest it, but he has to consider it. They have to explore all the possibilities. This was the same reason they had to interrogate Bobby Rupp. Maybe he lost it over Herb's meddling in his relationship with Nancy.
Church's lead was of a similar nature. He too, had heard of someone admittedly hostile to Mr. Clutter: a certain Mr. Smith […] who believed that the squire of River Valley Farm had shot and killed Smith's hunting dog. (1.25)
Would you slaughter a family because you suspected that someone killed your dog? Most of the investigators suspected that the family was killed by someone angry with Herb Clutter about something. But a dog?
"There's got to be something wrong with somebody who'd do a thing like that," Perry said.
"Deal me out, baby," Dick said. "I'm a normal." And Dick meant what he said. He thought himself as balanced, as sane as anyone—maybe a bit smarter than the average fellow, that's all. But Perry—there was, in Dick's opinion," something wrong" with Little Perry. (2.106)
Who's more dangerous—the guy who thinks he's perfectly sane after killing a family of four, or the one who questions his sanity? For all Perry's craziness, he does have a little insight into his behavior.
All that belonged to him, Dick, but he would never have it why should that sonofab**** have everything, while he had nothing? Why should that "big-shot bastard" have all the luck? With a knife in his hand, he, Dick, had power. Big-shot bastards like that had better be careful or he might "open them up and let a little of their luck spill on the floor." (3.209)
Since Dick feels people are rich because of luck, not because they earned it, he feels entitled to take it from them. Herb Clutter was the victim of this kind of envy and bitterness. But you also see Dick's sense of powerlessness in life. It takes a knife to solve that problem.
I still think the reason he started doing stunts such as that was connected with the smash-up. Concussed his head in a car smash-up. After that, he wasn't the same boy. Gambling, writing bad checks, I never knew him to do them things before. (3.22)
Dick's father was way ahead of his time. Now that scientists can look inside the brain, they're looking at what kinds of brain damage might lead to criminal behavior by affecting aggression and impulse control. Think about all those former NFL players who attacked their families or killed themselves because of repeated blows to the head. Because of the M'Naghten rule, the defense psychiatrist wasn't even allowed to present his suggestion that brain damage couldn't be ruled out in Dick's case.
I started drinking, and was drunk for almost a month. I neglected my business, spent more money than I earned, wrote bad checks, and in the end became a thief. For this last I was sent to the penitentiary […]. (4.64)
Dick thinks everything started with his drinking, which eventually led to criminal behavior. It's a slippery slope. We guess that murder was just the next logical step. Right.
"I was sore at Dick. The tough brass boy. But it wasn't Dick. Or the fear of being identified. I was willing to take the gamble. And it wasn't because of anything the Clutters did. They never hurt me. Like other people. Like people have all my life. Maybe it's just the Clutters were the ones that had to pay for it." (4.121)
Wow. Perry tells it like he sees it. It was a lifetime of trauma that led to this horrible crime. Capote and the court psychiatrist appear to agree with Perry on this one.
'It's a rotten world," Latham said. There's no answer to it but meanness. That's all anybody understands—meanness. Burn down the man's barn—he'll understand that. Poison his dog. Kill him." Ronnie said Latham was "one-hundred percent correct," adding, "Anyway, anybody you kill, you're doing them a favor." (4.243)
"[…] why did you do it?" And York, with a self-congratulatory grin, answers, "We hate the world." (4.248)