riker disintegrates yuta after 3 phaser blasts dont stop her. she continues to try and kill her target. why didnt he just stun her? i took it as he tried higher levels of stun and that her physiology just made her immune to stun leaving just the final option that he had to kill her.
Perhaps even more significant is what Riker learns of the determination of Yuta. If the successive levels of stun and the certain knowledge that she has failed and will be stopped are not sufficient for making her surrender, then she is a goner. There isn't anything left in her head that would allow her to have a life of any sort if Riker merely stops her. Mercy killings don't seem to be morally objectionable to our heroes as such, so Riker probably engages in one here.
Of course, the Federation supposedly cures all criminals with counseling sessions (and possible Tantalus chair sessions), so there really ought to be some
hope for Yuta...
killing a defenseless and hopelessly out manned enemy is wrong.
Not if gunning him down is the only way to save Picard's life.
What people seem to be assuming is that the police chief had a stun mode available to her sidearm. But this is never established anywhere. To the contrary, the Rutians hope that the Federation will provide them with superweapons, Riker's own stun-capable sidearm supposedly being a prime example.
So Riker would be essentially saying "You could have aimed at his leg and merely crippled him for life!", which of course still is a silly thing to say because attempts at Wild West marksmanship would probably have led to Picard's death.