But even if only 1 did it and the other 2 just stood there and didn't move (which is already a non-realistic scenario), the ones who didn't do it, but were present and didn't report the crime, that already makes them accomplices, couldn't they have charged them with complicity to murder at least, if they don't know who played the most active part in the actual killing? The same in the Hells Angels case.

Because, for example in Italy and USA, if a murder is proven to be the result of the Commission meeting (or whatever group of bosses who take a group decision or vote to kill somebody), they all all considered guilty if the meeting where the murder was decided is proven to have taken place, and all the defendants are proven to have been present. Even if somebody voted against the hit, but was overruled by the majority, he is considered guilty at least as an accomplice, because of doing nothing to prevent the crime, not even making an anonymous call to the police.
Like Carmine Persico who was supposed to have voted against the Galante hit and was overruled by the other 3 votes, but still got 100 years.
I know, recently they said that maybe it was DiBella who voted and not him or that there was no Commission meeting at all, but just Rastelli ordering the hit by himself, but you get my point, what I mean.....If somebody can't be proven as having directly pulled the drigger or personally stabbed somebody, or explicitly said "kill him", there are still ways to link him to the crime as an accomplice, and here they charged them only for dismembering the body....So, if they had just thrown the body into the water, they wouldn't have received even suspended sentences? I don't know the Dutch laws, but it's weird in this case.....

The only equally absurd case that I remember was about a serial killer in some Latin American country (maybe Ecuador or Honduras, I don't remember) who killed hundreds of people, but the maximum penalty allowed for murder by the law was 15 years only, so they released him after serving that!!! No similar murders have been reported after that though, hopefully the police gave a tip to the local people who "made him disappear", don't know....Forgot the bastard's name, only that he was on Wikipedia apart from normal articles, so must be a known one.