Maybe in some sense you aren't responsible, but don't you want to be responsible?
And the things that you want, therefore are. So take credit for killing that Paladin! Who is going to say otherwise, a dead Paladin?
Well, as a basic principle people should be paying attention to traffic. But as a basic-er principle, people should always be looking out for opportunities to kill Paladins.
I mean, do players even know what they are doing half the time? Most players are like dogs chasing cars. They wouldn't know what to do if they caught one- they just, you know, do things. "I wanna roll some dice and see what happens! Whaddya mean, launching a fireball in a 10' x 10' room isn't a great idea? FIREBALLS ARE ALWAYS A GREAT IDEA!"
But all of this aside, how you approach it is up to you, but I would say that in the end, it doesn't matter much. Trying to import current legal standards (and ideas about culpability and mens rea) into a made-up, pseudo-medieval world doesn't make much sense, for the most part. I mean, for some time there was idea of guilt that was attached to the object (look up deodand some day if you're curious) and many early societies had a conception of what we would call "strict liability" for a lot of their criminal, civil, and ecclesiastical law- the idea that the consequence was your responsibility, regardless of your intent.
But does it matter? It's a game. No one (I HOPE!) is playing Lawyers and Liches.
So what you're saying is that if you push a paladin off a cliff so that it lands on a gnome, the paladin would be considered a deodand and literally given to god?