I think you're right there, if the soul could be translated as "conscience", or the ability to empathise with other people. The true psycopath does not have this ability, even non-psycopathic pattern offenders have less empathy and are able more easily to reason away the bit they do have to square things up with themselves.
I've been looking at the nurture verses nature issue lately, and whether psycopathy that leads to violent physical or sexual offenses has any real biological basis. I've not quite assimilated all the information yet, but there definitely seems to be more of a "nature" problem than a "nurture" one. Serial killers brains do usually have faults from birth, or lesions from other later traumas on the frontal lobes, the "conscience" area that helps people modify their natural instincts.
Obviously an abusive upbringing can bring out the worst in a child, or maybe surface later on in life, but the predisposition seems to already be there for these types, after all not all abused people go on to become abusive to others, physically or sexually, or even verbally.
One "nurture" factor that does seem to have a bearing is whether the person in question was properly bonded as an infant. Serial killers have a much higher incidence of maternal non-bonding than other types of offenders. Perhaps the infant had to spend a great deal of time in a hospital or other institution, or was seriously neglected company-wise in the home. Infants that don't make a specific bond with their main carers have a much more difficult time connecting on an every day levelwith others.
I'm not sure there can be one standard simple explanation for why a particular person becomes a serial killer, but there does appear to be a core of basic factors, the majority of which are biological, one or more of which are present in virtually every case of psycopathic pattern offense, particularly of a sexual type.
Does anyone have more information on the study of the damaged frontal lobes, I'd be really interested to hear it