Look, everyone here is posting their opinions. In the Peru case, other than the video snippets (which can easily appear out of context, considering that the video runs constantly and we haven't seen any of that), all any of you are doing is speculating about WHY Joran killed Stephany. You take it for granted that he did kill her, without any hard evidence that he did so.
My points about the ever changing state of the crime scene evidence have been ignored. This is crucial stuff- position of body, murder weapon, wounds, etc. A few mistakes happen in every case, but they are invariably corrected pretty quickly. The ones in this case are still occuring (as of just a few days ago, when we suddenly learned that Joran actually strangled Stephany to death with his own shirt). A solid system of justice is based on understanding principles that we should all hold dear; certainly, emulating a system like Peru's would ensure less violent criminals on the streets. It would also ensure more innocent people in prison.
As for the Holloway case, there is no evidence to connect him to the death of Natalee. That's because there is no evidence that a crime was even committed. She disappeared without a trace, and nothing has been found of her since then. Of course, logic compels the supposition that something happened to her, but without a body, or any forensic evidence at all, Aruba could not convict Joran or anyone else of a crime it can't prove happened. Now, perhaps Peru could manage to do that.
My speculation is just the same as most of yours, just not as popular.