Player x accuses player y for breaking NLR, the kills are pretty close together in console (a few lines apart) at a peak time.
First I would bring player X to me. I would ask him to tell his story. Then I would bring player Y to us and ask him to do the same. If their stories matches, and if it was RDM, I would warn player X for RDM. But if player X was raiding/mugging player Y, and player Y broke NLR, I would warn him for NLR.

You were asked , how would you handle the situation if a player accuses another player for breaking NLR, not RDM.