Its interesting how often my choosing a "random" episode brings me back to this one. This episode has marvelous guest stars. One is Marc Lawrence who is killed by Yuta at the meeting of The Gatherers, 50 years earlier he was usually playing the bad guy in many WW2 era films. I really enjoy the performance of Nancy Parsons, her Sovereign Maruk is both regal and overbearing with a nasty temper but she clearly wants to make this treaty work. Stephen Lee makes a great counterpart to the Parent role of Maruk, playing the childish and petulant Chorgon, who actually succeeds in bringing some good lines out of Wesley, no easy task. Yuta and Riker share some interesting conversations, I like where they decide that Riker would make a lousy Monarch and Riker happily agrees. His "Parthos a la Yuta" was a good line, too bad he only ate a bite of it. This is the sort of thing the show should have referred back to as it progressed, with Riker ordering some Parthos from his personal replicator "favorites" now and again. Naturally the ending remains controversial. Yuta still carries the killer virus and is trying to kill the remaining clan member. Its reasonable that Riker would have to stop that, and we know what he does. Zzzzzzzap! Was that needed? Unfortunately I don't think it holds up, all through the episode we are told that the killer virus is engineered to only attack the members of a specific clan. Its not like Yuta has explosives in her undies, nobody at that table other than Chorgon is in any danger and Riker could simply walk over and get in the way so she couldn't touch him. Just push her out of the way. Tell Chorgon to move to the other side of the room. Beam Chorgon or Yuta up to the ship instead of beaming Riker down. Nope... Its almost like at the last minute they wanted to make the whole script more serious or "adult" by using this ending. We're supposed to feel with Riker over his choice, and if it was his only choice that would be fine, but it wasn't. Also, Data solving the whole puzzle based on being able to see Yutas obscured face in an old photo is a bit convenient.
I'm critical of Riker for a lot of things he does, but killing Yuta isn't one of them. He progressively raised the setting on his phaser, yet despite getting shot each time, she continued to try and kill Chorgon. She could have stopped at any moment, she deliberately forced the situation and continued to force it.
There was a pause where they looked each other right in the eye. She knew Riker had cranked up the juice and wouldn't hesitate to fire again. She knew her time was up and went willingly. Either because her vengeance program mattered most, or she thought there was no future worth living even if she spared Chorgon. But yes, Riker could have put the smack down and stopped her that day and removed the choice. Then they toss her in prison for a thousand years of counseling or they simply sentence her to death and somebody Else plays executioner.
Kassidy got a year tops for smuggling for a terrorist organization, Garak got six months(which he didn't even serve all of as early as he appeared next season) for attempted genocide and inciting a war, and Bashir's dad got two years for genetic engineering which was described as harsh. Chances are Federation court would let her out in a few weeks for something as minor as attempted murder.
I sometimes wonder if there were a genetic component of Yuta's alterations that would have prevented her from trying to do otherwise. She says at one point that she has no choice in the matter, but doesn't elaborate on whether that's the case from a biological perspective. But it would make sense from a weapon design standpoint.
As long as Yuta was alive, she could try again. Prison would be ineffective - she could escape and go after Chorgan as many times as she wanted. They couldn't take that risk. Riker did not murder Yuta - he killed her to defend Chorgan's life. That is not, and never will be, murder. Defense of self or others is absolutely allowed.
It's only justifiable if there was no other way. Given that Yuta was sent reeling by the previous blast and only barely managed to get up, hit her with another one, a sustained blast, and she'd be sent sprawling. In any case, I can't believe that one setting will send her stumbling and the next setting up would vaporize her. There will be SOME setting that will knock her out. And as for her punishment, well, put her on a planet with no way off, and she won't be much of a threat. We saw in classic Trek that there are any number of prison worlds that make sure that prisoners have no access to the supply ships.
The scene at the end of the episode, with a self-tortured Riker--knowing what he did was right, but still hating having to have done it--turning the glass around and around as he stared ahead with that awful look on his face is a high point in the series. And having Picard's subsequent line (not saying anything about the incident, but clearly trying to help Riker put it behind him) was also spot on. It was episodes like this that got me excited about watching ST again, more excited than I had been since watching 1st and 2nd season syndicated reruns of TOS.
It's possible that if she were restrained she could have faced justice or even been rehabilitated. You can't just wipe out anyone who may pose a risk to someone else. Especially since Riker had feelings for this person, it's just a bit odd that he would crank the phaser to vaporize.
This was an internal matter of the warring factions. Whatever one may think of Riker's actions, she would have answered to local law, not the Federation's.