Why did Truman Capote title his book "In Cold Blood"? Was it because of the characters' upbringing, which in their minds may have justified their...

Capote's
journalistic novel chronicles the robbery attempt by Richard Eugene Hickock and Perry Edward
Smith, a plan that Hickock devised while incarcerated.  While in a Kansas prison Hickock had
heard from another inmate that Herb Clutter for whom he had worked at one time, kept large
amounts of cash in his home safe.  With Smith, Hickock planned to rob the Clutters of their
money.

On November 14,1959, after driving across Kansas, Hickock and Smith
attempted to rob Clutter, but upon learning that he paid all his bills by check and had
virtually no money in the house, Smith coldly slit his throat and then shot him in his head. 
When interviewed, Perry Smith said,

I didn't want to harm
the man.  I thought he was a very nice gentleman.  Soft spoken.  I thought so right up to the
moment I cut his throat.

After Smith shot Clutter, he put
a single shotgun blast into the heads of the remaining family members.  This was the first mass
murder of such brutality committed in the United States.  Smith's senseless and brutal,
cold-blooded killing of the Clutter family and Smith's obvious detachment of feeling and
psychoses, Capote was prompted to use the phrase "cold blood" in his title.

During Perry's incarceration after his trial, Capote visited him constantly, having
bribed the officials into giving him carte blanche to
come and go as he wished.  Smith, a child of institutions had many stages of his development
arrested in the infantile stage:  he wet the bed, sucked his thumb, and cried out for
"Daddy" in his sleep.  He prefered root beer to beer or coffee.  Being of mixed
heritage, Indian and Irish, Perry had many psychological problems that Capote found fascinating,
and, perhaps, felt were the cause of Smith's detached, cold killing of his
victims.