I did not realize they were criminally insane. I thought they were guilty of murder, period. 
 Maybe sociopaths or psychopath ?
They certainly knew what they did was wrong. 
I have no idea about who the people were in their llives but if they are sociopaths or psychopaths, it's unlikely it would have made a difference.
I heard an older judge from Minnesota who had been on the bench for 35 years sum up offenders in three groups.  
The NORPS, Slugs and Slickees.
The Normal Ordinary Responsible Person is someone who has no prior record but goes out one night has too much to drink and pees in flower pot at a classy restaurant. He is unlikely to ever be a repeat offended and being arrested is a huge consequence for him.
 A Slug is the repeat offender who is slow to learn from his experiences without a great deal of "education". 
A Slickee rarely gets caught because they are sociopathic and deceptive.
http://www.legis.nd.gov/files/committees/63-2013nma/appendices/15_5079_03000appendixd.pdf