Any comment on the bigger picture? I've seen questions asking for the one point that tipped the scales ... but anyone that has followed the case knows that it was a circumstantial case supported by DNA evidence.
Rudy was one of the people that Amanda befriended when she arrived in Perugia. She later met Raffaele and quickly befriended him too. She also befriended one of the guys that lived in the downstairs flat. It's interesting to note that one thing all of Amanda's new friends had in common was illegal drug use. Chances are that if she were not roommates with Meredith, they would never have met - as Meredith was not drawn to her as a friend, they had different social circles, and did not attend the same school. For Amanda to get together with two guys that she had come to know while getting stoned in Perugia is nothing strange ... she had been in Perugia less than a month and they were her first friends (Meredith was distancing herself from Knox). Meredith and Knox both spoke English, but they had little else in common.
The two men met through Amanda. They most likely consumed drugs together ... since they all like drugs. They did not enter a conspiracy, but instead there is the possibility that Amanda decided to play a prank on Meredith (she was known to pull sick pranks on people when she lived in Seattle) and got Rudy and Raffaele on board. After letting Rudy and Raffaele in through the front door, it's possible they smoked some more, or drank some more, and then decided to have some fun with Meredith. Meredith was tired; having been out late celebrating Halloween the previous evening, and had borrowed a textbook to prepare for an exam. She had to return the textbook the following day. Meredith was probably in no mood for Amanda bringing men to the cottage. It was her home, not a party house for Knox to use while she lived with Raffaele. According to Rudy, Meredith, who had rent money in her room but had not yet given it to Filomina, confronted Amanda about missing money. We don't know if this is true. Something went wrong, whether it was a prank, or Meredith confronted Amanda (men visiting, noise, missing money???) which ultimately led to Meredith's assault and murder. The three then took Meredith's two cell phones and ran away. It looks as though Rudy ran home (the clamouring up the metal staircase while the other footsteps ran away), changed and then went clubbing, while Amanda and Raffaele probably smooched a bit, and then decided to return to the cottage and clean up the scene. There was reportedly no activity on Raffaele's computer at this time.
It looks as though they took the lamp from Amanda's room and put it on the floor to look for something. It was also discussed, long ago, that the blood pooling in Meredith was on her shoulder, yet she was found in a prone position covered with a duvet - suggesting that she was moved after she died. At some point, Amanda and Raffaele took the keys, locked the bedroom door, staged a break-in but ransacked the room before breaking the window (another oops), cleaned up and left.
When they realized they'd left the lamp in the room, they tried to break down the door but only cracked it. When Filomina and police arrived, Amanda was tossing between frantically running around the cottage looking for the boys (even though she first denied and then admitted that she knew they were away) or ways to get into Meredith's room and claiming that Meredith routinely locked her bedroom door so there was no reason to break the door. Police did not want to break the door because of liability issues. Filomina disagreed with Amanda and insisted that the door be broken, at which time everyone was huddled around the door except for Raffaele and Amanda ... who were in the kitchen ... while a friend of Filomina broke down the door to find Meredith on the floor with only one foot exposed under the duvet.
