I think it goes beyond neutrality, or curiosity. Some seem to have a rather urgent drive towards it. In this case it seems like there's a sexual element as well.

Aside from the vehement distaste I feel towards these abominations, they're also fascinating, in that they seem alien to me.

How does one come about? Does it feel and think as I do? How different is its experience of the world as compared to mine? Is it different on the same level as the hypothetical difference in perception between the sexes? Or is it further removed—as the perception of the world would be different for a bat, say.

Does it have a purpose in nature to perform some kind of function? Or is it a failed experimentation (mutation) on nature's part; over-optimizing certain things leading to "unintentional" suboptimization of other things? Or has it more to do with nurture rather than nature?

The fascination is directly proportional to how hard it is to comprehend this.

He did go through a physiological test and the report says he is sane and do not qualify the definition of psychological ill, but then the report says in the next meaning he is a psychopath with narcissistic behavior, pathological lies and with a severe sexual deviation.

Trying to understand why a sane person would commit such crime is impossible, so I personally consider that what we have heard and seen is not the behavior of a sane person. Trying to frame it like a video game is trying to impose rules of sanity to explain insanity.

The judge thought it was pre-meditated. He had extra tools on board of the sub, that usually stayed in his workshop. He had also contacted multiple women in the time up to the killing, asking them to go on a trip with him in the sub. The day before he killed, maimed, and dismembered Kim, he watched a genuine snuff film, on his computer, showing a woman getting killed.

He is up to something like three or four different explanations for an accident, and they have all been refuted by experts. Also his psyc evaluation concluded that he is a danger for others.

I'm sorry but I find your apologetic tone uncomfortable.

There is evidence that it was premeditated. From the article:

> They [the jury] heard how he had joked about “a murder plan” involving tying up a woman on his submarine and slitting their throat with a knife in a set of messages sent to a friend, which he had subsequently tried to delete.

Considering he mentioned wanting to do exactly what he did (slit a woman's throat and kill her on his sub) before he ever met wall. I would go with it was premeditated. "They heard how he had joked about “a murder plan” involving tying up a woman on his submarine and slitting their throat with a knife in a set of messages sent to a friend, which he had subsequently tried to delete." Note, he tried to delete these.

He also changed his story multiple times. Beginning with dropping her off on shore alive, to dropping a hatch on her head and finally carbon-monoxide poisoning.

One of the reasons we don't have the full story is that Madsen has repeatedly lied about it, in ways that can be verified. The general drift of those lies has been to make it seem like an accident, so we can reasonably assume that the truth does not indicate that it was accidental.

Edit: Thanks to several people for pointing out large gaps in my knowledge of the case, sounds very much pre-meditated!