No. If you take a look around, you'll notice that if the murderer is discovered he/she gets a relations penalty with other characters (not all, but for example with the victim's close kin, I don't know the details). So no, it's not the game telling the player things that are an out-of character knowledge. The other characters know it as well.
As for the original topic:
To everyone that thinks the current situation is fine.
Imagine, if you will, two scenarios:
One: King Olaf’s son has been murdered and mayor Adalbert has been apprehended as the men behind the murder. King Olaf has called for all of his vassals to arrive at court in Anhalt to listen to his judgment.
‘Lords of Denmark’ said King Olaf ‘I have summoned you all here to bear witness to my judgment. My son’s murderer, mayor Adalbert is to be released at once from my prison’
For a moment there was silence, and then the great hall exploded with cries of joy. Count Herbert has renounced his claims to independence, Duke Folkmar has agreed to pay higher taxes, Archbishop Eberhard has promised to stop paying taxes to the pope and to send it to the king instead, Baron Werner has decided to send more of his men to his liege’s service.
King Olaf rose from his throne
‘Shut up!’ he yelled A of you, have you not heard what I just said? A men who murdered my son is going to walk away free. If the life of a Prince of Denmark is worth so little, how much do you think your own lives are worth? I basically just told every single vassal or courtier in the realm that they are free to plot, scheme and above all murder as they please.’
For a moment there was silence, and then the great hall exploded with cries of joy. Count Herbert has renounced his claims to independence, Duke Folkmar has agreed to pay higher taxes, Archbishop Eberhard has promised to stop paying taxes to the pope and to send it to the king instead, Baron Werner has decided to send more of his men to his liege’s service.
Two: King Olaf is eating a meal with his brothers: Count Kuno and Baron Gerhard. The atmosphere is gloomy – their mother has recently been murder at the orders of Count Dietwin.
‘My King, brother’ said count Kuno ‘there’s something I want to talk about. It’s about our mother’s murderer’
King Olaf gave his brother a long deep look and then said:
‘He’s been imprisoned and awaits my judgment’
‘Yes’ said Kuno ‘so I’ve heard. You see, the thing is…’
‘You should let him go’ finished Gerhard’
‘What?’ King Olaf’s face was a mixture of disbelief and outrage.
‘You heard me well brother’ said Gerhard ‘Dietwin must be released from your prison’.
‘Yes’ added Kuno ‘Don’t get us wrong brother, me and Gerhard, we really loved our mother, but it’s just not right, I mean he didn’t like do anything, right I’m not sure we should even tolerate the fact that you imprisoned him’.
King Olaf clenched hid fists.
‘He will die’
‘I don’t think that’s a good idea, brother’ said Kuno ‘If you kill him, this may very well cost you your kingdom. Granted, nobody really likes Dietwin, he’s the most prestigious member of his dynasty, he has no friends and his conspirators were mostly random courtiers and bishops, but if you execute him… Well, let me put it this way: do you want Pomeralia to start a war of independence? Do you want your bishops to start paying taxes to the Pope? Do you want for half of your vassals to start a war to lower the authority the Danish crown holds? If so, then go ahead and kill Dietwin’
That’s how it works right now.