Musing about this whole thing, I find it strange the level of cleverness that people attribute to RG, but at the same time the level of dumbness.
1. He's not agile or clever enough to scale the wall or break the window. He must be let in the door by AK.
YouTube - ‪Bad 

Wall Climb (Parkour)‬‏
2. He's not clever or charming enough to talk his way into the house, because MK would never let him inside.
3. He's not clever enough to clean up his own footprints and evidence or flush the toilet before he leaves.
4. He's not sensitive or guilty enough to cover MK or lock her door.
6. He lacks the common sense that leads him to say he told his friends about his date with MK when in fact, he did not. He lacks the common sense to know her friends would not back up his stories that he'd been with MK at other parties. He's not sharp enough to figure his friends wouldn't back up any of his claims.
And yet,
1. He's clever enough to devise a story that will not implicate him or direclty implicate his "co-conspirators."
2. He's witty enough to say "Wasn't me" in the CCTV video, and people believe it.
3. He's sharp enough to confuse the time of death by saying he arrived actually 45-50 minutes before the death. This is, in fact, his biggest ruse, since he openly says he arrived early, cased the joint, saw no one there, and returned at 838pm to wait around for his "date." He then says MK was dead by 930pm. And he's so clever that no one believed him when he told the truth.
4. He's smart enough to claim the window wasn't broken and charmingly convincing enough that people actually believe him despite the fact the he actually carried rocks for the window breaking task in his bookbag (so I heard.)
5. He's clever enough to never discuss his crime in jail, like so many other criminals do, and smart enough to pen a letter of denial in handwriting COMPLETELY different from his jail diary. Then clever enough to say he can't read his own writing in court, so that he doesn't put his false statement into evidence himself.
Letter:
http://www.tgcom.mediaset.it/cronaca/articoli/articolo476174.shtml
diary:
http://truejustice.org/ee/documents/perugia/RudysPrisonDiary.pdf
6. And, after all these years, he's been able to hide the secret behind the fact that he, RS, and AK were actually friends to the end who'd never turn on each other---except, wait, is that a shadow I see in the yard?
The man is just brilliant---and stupid at the same time.....