To be fair you just done a pretty good summing up for the prosecution there but with respect its not completely impartial to the facts.
The court did hear that at some point Libby had expressed an idea of suicide by drowning in a river?
The affection (apparently) shown to PR wasn't completely out of character for her that night, according to another witness she was asking them to lie down with her and hug her and became verbally abusive when they refused.
Her behaviour or thoughts on that night cannot really be logically explained because she quite clearly wasn't thinking straight in terms of logical rational behaviour, might she not have simply gone home initially when she had the chance if that was the case?
You are also missing out the option that perhaps she could have gone into the river accidentally (by misadventure) not intentionally or with suicidal tendencies, but indeed by her own hand/legs.
I'm predominantly playing the devils advocate position here, I do believe he was ultimately responsible but its only "fair" to put the facts together as they actually were presented.
Ok to counter devil's advocate
For point one - she had been discharged by the mental health services as requiring no further follow ups or action. Her friends had given evidence that she was happy and joking at a party that night. None had any reason to believe there was anything amiss in the period running up to it. She had contacted her long term boyfriend at 10.30 that night. She had discussed the following days lecture with a fellow philosophy student. She was seen by several witnesses to be very drunk and by an expert to be hypothermic. Nobody thought her suicidal.
As her friends had no reason to lie we can assume they are telling the truth. Her behaviour was typical of a drunken hypothermic person therefore no other factors can be reasonable assumed.
For point two her behaviour changes alarmingly with PR who has lied throughout this. But even if he was correct several witnesses and an expert have stated she was extremely vulnerable and certainly not capable of consent. Anyone of the men she came across - including the students - could have raped her and chose not to.
We don't know the full context of her earlier interactions so they could have been to get warm
Last point - we were told by the expert her body temperature would mean she would find it difficult to run and we saw she was struggling to walk on the street.
PR takes her to a park and raped her
If he hasn't taken her close to the river to do this she then has to to walk to it herself. If her adrenaline kicked which I'm not sure if would if hypothermic - she head to the houses not in the opposite direction. Bang on a door
If adrenaline hasn't kicked in and shes not near the river she has to get there herself. The terrain is rough. It's location she doesn't know (unlike PR). She avoids a massive pond. She doesn't turn and head for houses. She manages not to lose her pants and jacket there but keeps them safe losing until after she's fallen in. She doesn't snag clothing on the many brambles the police removed.. She would have to walk uphill at some points.
If on the other hand he has taken her close to the river the problems with timing disappear. It wouldn't take much more time to put her in a river.
In short either she walks all thru the park after the rape away from housing without losing the pants she's carrying on the way or leaving any evidence such as a lost shoe. Or he walks thru the park
So if the timing goes what else to consider.
Why did PR take her to that point to rape her in the park when he could have raped her in the Endsleigh centre or his warm car. His uncontrollable urges were pretty controlled in that respect.
Why did PR go to the park earlier at 9.45 pm. And return at 2.24 am.
Why did he prowl around the student area afterwards?
Why did he feel secure enough to fill a condom with semen after his second prowl around - knowing that she would report him and be a witness to location and description. A rape would be taken more seriously then his previous 'silly' crimes and with his DNA already on their database he'd be in big trouble?
I must admit his lack of empathy is quite chilling and is a psychopathic trait. His later prowling is also chilling