I have been thinking about the different theories of what had happened, that has come up here in this thread.
My own theory is that it must be planned, but I am always open for other views of the case, as long as the dots can be connected. In my own theory I can connect the dots, so thats why I believe in that.
The theory about it being an accident and that PM must have panicked about losing his lifes work is something I have a hard time with connecting the dots. I will try to explain why here.
1. argument: There was a fatal accident and PM felt he had to hide it, because he was afraid of losing his lifes work.
2. argument: He had to dismember the body to get it out of the submarine.
3. argument: He sank his submarine deliberately after he was discovered on the sea.
This last argument is exactly what I cant connect with the other arguments. Why would he want to sink the submarine if it is so important for him so he dismember a body just to save the submarine and the work on it?
It doesnt connect. I cant get into my head why he would do that.
Maybe someone here can find the connection and explain to me?
The only reason for scuttling UC3 Nautilus must be that he couldn't clean it (disappear the evidence - he probably didn't think it would be salvaged). Dismembering the body of a recently deceased is an extremely bloody and messy affair. Despite having been filled with seawater for some 24 hours police technicians actually still found traces of Kim Wall's blood.
We don't know what time Kim Wall died, or what time Peter Madsen disposed of the body, but it's at least safe to assume she was dead before her boyfriend contacted the Swedish police. That was 3:40AM, and the UC3 Nautilus was sunk 10:30AM. Sunrise is just before 6AM, so likely Peter Madsen had disposed of the body by then. However, Peter Madsen initially claimed he put Kim Wall ashore at 10:30PM, which could very well have been what they originally planned (3-4 hours of sailing/interview). I will therefore conclude Kim Wall was dead by 10:30PM, and Peter Madsen spent the next 12 hours trying to come up with a plan. This is where the idea of a planned murder doesn't fit. If you plan to murder someone you (likely) include a way to dispose of the body. It was, in fact, the long absence that led police to suspect Peter Madsen. He would have known that the authorities would come looking for a missing submarine in Øresund (UC3 Nautilus was reported missing by one of Peter's friends around the same time Kim Wall was reported missing). Also, the police normally don't start looking for a missing adult before that person has been missing for 24 hours - at least. Initially they weren't looking for Kim Wall, they were looking for UC3 Nautilus. If he had simply returned to Copenhagen, moored UC3 Nautilus, and told the police he dropped Kim Wall off at 10:30PM, he would probably have had another day or two before police would suspect foul play. In short, killing someone on a submarine and then sailing around until the maritime rescue authorities start looking for you is without doubt the worst plan ever.
There is another thing here. Peter Madsen didn't sink UC3 Nautilus until a private motor boat came up alongside her. He shouted to them that he was heading for Copenhagen harbor (he
was heading that way) with a technical problem, and asked them to stand by. He disappeared below deck for a moment, then popped back up as the submarine began to sink. What would he have done if the motor boat hadn't arrived? Would he had continued to Copenhagen, or was he waiting for a boat to come close? The whole thing stinks of panic.
My belief is that Kim Wall died (either murdered, or by accident) before 10:30PM August 10, and Peter Madsen had no idea what to do next. He sailed around for some time trying to find a way out, and eventually decided to dispose of her body by dismembering it and dumping it in the sea. He would likely have spent many hours trying to clean the submarine without success. The idea of scuttling UC3 Nautilus might have been brewing, but I don't think it was truly formed before he saw the motorboat. Otherwise he would either have waited around over deeper water (where salvage would be difficult) until someone came close (it's a very busy area), or simply scuttled her while nobody was watching (swimming ashore and claiming he didn't know exactly where UC3 Nautilus was).