It's Rudy's presence that's the problem. Most low-info people (who can tell Amanda's guilty by her evil eyes) don't even know he exists. If they do know they assume he was a well established chum of Amanda's. But his only connection with Amanda is of physical proximity, he occupied the same space as her for several moments because he was loosely acquainted with someone who lived in another unit at the residence.
So he in no way could be involved in an intricate murder plot. It simply doesn't work, and is why no court ever proposed such an idea. You can't have Amanda spontaneously running into a virtual stranger she can't even communicate with an adding him to a carefully plotted murder scheme.
The official culpable series of events tries to stay within the boundaries of reality. Amanda happens to run into Rudy and invites him along as a loose acquaintance for a potential social gathering, or he just said he wanted to walk to the cottage with them to see if his friend was home, or whatever. And once they all get there "things get out of hand" and Meredith ends up dead. Of course this scenario doesn't work with the kitchen knife, and since the kitchen knife is the entire case, going with this scenario is essentially admitting reasonable doubt out the starting gate. The Italians, lacking any sense of logic or judicial restraint, tried to get around this by saying Amanda carries a gigantic comically sized kitchen knife around with her at all times for no reason, but this was never going to withstand any real scrutiny.
Exactly. Having a furious row with a room mate doesn't lead to murder, unless the assailants have armed themselves in advance (=premeditation). Raff was armed up to the gills with lethal fetish-style knives, some costing >€250-. His public myspace fantasy was to have 'extreme experiences', he had a heavy drug problem, liked to pose as a mad-scientist-butcher wielding a meat cleaver. He was so irresponsible, his father had to ring him several times a day to monitor him (a grown man of 23, three years older than Rudy and Amanda).
Amanda went to Italy to, by her own account, get lots of sexual experience, and was there to party. Mez was everything she was not. Classy, more attractive, better educated, nicer, cleaner and far more popular. The only people on Amanda's speed dial were the various men she slept with. The void she wanted to escape when she fled Seattle to have fun was still there, a gaping hole in her damaged psyche.
So, rich boyfriend with own flat, cleaning lady and latest Audi, shares his violent sex manga fantasies, which coincide with her own (cf: school essays about violent rape/murder), Amanda is desperate to please him. She bends his ear about Mez and how much she is screwed up with jealousy and hatred for her, because Mez shook a great mojito and Patrick wanted to hire her instead and had a great social life, was part of an accredited ERASMUS course, hooked up with Giacomo, which Amanda resented, believing she had first rights to him ("You can have him") not to mention revelling in her German "Nazi within" and with Mez being Anglo-Indian, had an underlying racist resentment as well. She referred to her boss as 'an African ragazzo' and had no hesitation in putting his name forward to the police as the rapist/murderer of Mez. Like many sociopaths, Amanda has delusions of grandeur. A grifter with the fast talk, a con merchant with instinctive acting skills, having become aware normal people act differently from herself and learning how to mimic normal behaviour. Hence all the theatrics in court and outside the court after verdicts of acquittal, mimicing an Oscar winning actress with her hands clasped in fake gratitude.
Like everybody else Amanda met, Rudy was just there to be used and abused. Even Raff was cuckolded in their five-day affair. Rudy claims Amanda flirted with him downstairs with the boys, certainly, he was around the cottage like a salivating dog, and he told Franca he was there more for Amanda than Mez. Kokomani testified the three were together getting off their heads on skank weed, wielding a kitchen knife and offering him €250- to hire his car.
A sociopath doesn't form close relations with people so there is no prerequisite for her to have any deep relationship with either Rudy or Raff, or indeed even the murder victim. It was no problem for Bonnie and Clyde to shoot dead random policemen in their way. They were just cardboard cutouts to these people, not people with homes and family.
You need to grasp that psychopaths are not normal so it is useless to use 'normal' as a term of reference.