No evidence to support your assertion that either Knox or Sollecito were/are psychopaths. For all your comparisons you ignore the fact that these are well liked we'll adjusted people.
Yes. Let's have a look, shall we, at Brenda Spencer, the school-age girl responsible for the infamous "I don't like Mondays" (NB: not "Monday") shootings. And then we can perhaps compare and contrast with the known history of Knox and/or Sollecito prior to the date of the Kercher murder (my bolding for emphasis):
Brenda Spencer (born April 3, 1962) lived in the San Carlos neighborhood of San Diego, California, in a house across the street from Grover Cleveland Elementary School, San Diego Unified School District. Aged 16, she was 5'2" (157 cm) and had bright red hair. She is said to have self-identified as "having been gay from birth." After her parents separated, she lived with her father, Wallace Spencer, in virtual poverty; they slept on a single mattress on the living room floor, with empty alcohol bottles throughout the house.
Acquaintances said Spencer expressed hostility toward policemen, had talked about shooting one, and had talked of doing something big to get on TV. Although Spencer showed exceptional ability in photography, winning first prize in a Humane Society competition, she was generally uninterested in school; one teacher recalled frequently inquiring if she was awake in class. Later, during tests while she was in custody, it was discovered Spencer had an injury to the temporal lobe of her brain. It was attributed to an accident on her bicycle.
In early 1978, staff at a facility for problem pupils, to which Spencer had been referred for truancy, informed her parents that she was suicidal. That summer, Spencer, who was known to hunt birds in the neighborhood, was arrested for shooting out the windows of Cleveland Elementary with a BB gun, and burglary. In December, a psychiatric evaluation arranged by her probation officer recommended Spencer be admitted to a mental hospital for depression, but her father refused to give permission. For Christmas 1978, he gave her a Ruger 10/22 semi-automatic .22 caliber rifle with a telescopic sight and 500 rounds of ammunition. Spencer later said, "I asked for a radio and he bought me a gun." When asked why he might have done that, she answered, "I felt like he wanted me to kill myself."
https://en.wikipedia.org/wiki/Cleveland_Elementary_School_shooting_(San_Diego)
I think it's clear as day to any (reasonable, rational) person that the evidence of Brenda Spencer's upbringing and mental health state prior to her murder spree is....oooh......fairly close to 100% different to that of either Knox or Sollecito. Furthermore, Spencer exhibited the classic escalation of mental health issues, hatred for authority figures, and lead-up crimes of a more minor but highly relevant nature (in her case, burglary and shooting out of the windows of her school). All of this such escalation is a near-ubiquitous pattern for anyone who gets to the point of committing psychologically-motivated serious crimes such as murder (i.e. murder committed "for the fun of it", rather than, say, in the commission of another offence, or as a hot-blooded act*).
Simply put: had Knox and Sollecito truly constructed a plan that night to go over to the cottage and commit some nasty criminal act of violence/degradation upon Kercher - whether or not the original intention was murder itself - then there would have been clear evidence of these sorts of mental health issues and the classic escalation of violence and hatred within at least one of the two (and in fact almost certainly within both of them, given that they'd only even known each other for just over a week, and thus were nowhere remotely near building the required levels of mutual trust or dominant control....). There's absolutely no evidence that remotely matches the prior history of, say, an individual such as Brenda Spencer - and this in itself constitutes extremely strong evidence that neither Knox nor Sollecito ever carried out such a "thrill kill" attack.
* Note please (since I am confident that many pro-guilt commentators might be either too ignorant or too biassed to understand this nuance) that I'm talking about the requisite evidence of prior history for someone embarking on a "thrill kill" type of murder(s). Therefore, these rules do not explicitly apply to Guede as sole attacker/killer, since I think hardly anyone (least of all me) believes that Guede set out that evening with the aim of senselessly killing Kercher. Rather, Guede set out with the aim of burgling (US: burglarizing) the cottage, but was then unexpectedly interrupted by Kercher's return, and a confrontation ensued. It's my belief that Guede (as evidenced by his frequent rejection by women and his known harassment of women) then started to be overcome with a potent combination of fear and sexual lust..... and this resulted in his instigation of a sexual assault upon Kercher which evolved further into the stabbing (probably, IMO, when Kercher began to struggle as Guede started to carry out his sexual assault in earnest). And if that's anywhere near what really happened, then it's a completely different dynamic of crime, and there's no requirement for the types of extreme prior indicators that would be in place for someone deliberately setting out on a senseless "thrill kill" (though it's very likely that someone committing such a crime a) would have carried out more than one prior burglary, and b) would have tried and failed to carry out prior low-level physical/sexual assaults of women. Hmmmmmmmmm.........
