So far, we have briefly discussed what other prominent scholars have said regarding the reasons Nephi killed Laban, and have also shown the typical beliefs of the time in order to show the type of understanding and upbringing Nephi would have had at the time of his life. So now, after understanding a bit more where Nephi may have been coming from we can look at the actual events to explore our main question further.
In my previous post I first discussed Laban's actions against Laman directly, as well as the other brothers. Upon receiving the treasures from Lehi's son's, he sent his men after the brothers that they may "slay" them (1 Ne. 25-26). This action alone, according to Jewish law can be viewed as actions worthy of a death sentence. Here we must again speculate as to Nephi's views of these laws. It is reasonable that he would see these malicious actions as worthy of some sort of retribution. The extent of that retribution, of if Nephi felt it was necessary or plausible is mostly up to speculation. This may, however, shed some light onto Nephi's actions and willingness to kill Laban.
Furthermore, if Nephi was aware of such stories as was demonstrated in 2 Samuel 20 (Sheba leading the Israelites away) then when the spirit beckons to him that it would be "better that one man should perish than that a nation should dwindle and perish in unbelief" (1 Ne. 4:13), he remembers the results of Sheba leading away many. Again, it is likely, or at the very least, plausible that Nephi is aware of these stories and may draw some of his actions off of what he had known others to do.
Regardless of cultural influences of the time, and upbringing, etc. we must also consider Nephi directly. Is he a reliable narrator? How accurate is his account? I believe there are clues in the text that can shed light on these things.
I believe that if we are to analyze this scripture accurately, and from a Mormon perspective, we must exercise some sort of faith in its accuracy and importance. Not only did Nephi feel that it was important to write these details (for any number of reasons) but also Mormon felt it necessary to include in the abridgment of all the records. We then must assume that the events unfolded as they were written to the best of Nephi's knowledge. This, however, doesn't excuse Nephi in any way, and may help us understand his perception better according to his writing.
First, we understand that Nephi, for his part, had a strong testimony. This may not have been purely his own, but perhaps borrowed from his father, but it was strong. It would have been built through the first four chapters in Nephi as well. He follows his father unquestioningly, see's an angel and converses with the spirit. The events he had undergone show that he would have trusted the Lord.
We also must examine his writing style. I believe Eugene England was correct in assuming that there was post-justification in Nephi's writing. Nephi (and this is a huge part of the problem in answering this question) is often vague. He gives little details in any of this writing. But you get to his descriptions of Laban and the sword, and suddenly there is a change. This, more than anything, shows that in his wisdom of years, when writing this he is attempting to justify his actions to make sense to himself. He may have regretted, ultimately, killing Laban. And I think that we can't be too hard on Nephi here. At the time he was a young man, he had not had many of the experiences he later had and killing anyone would be a difficult task, regardless of whether or not it was commanded by God or not.
We also see how Nephi is critical in his responses to the Spirit. This Brad Kramer points out in that Nephi shrinks when told to kill Laban. Not only that, but he questions the spirit and demands repetition. We read multiple times, "the Spirit said unto me again." The "again" is important here, showing that Nephi did not simply shrug his shoulders, pick up the sword and slay Laban. He interrogated the Spirit. He had to be sure.
Does this justify the killing of Laban? I think not. I do not think it answers the question thoroughly enough to have a conclusive, "yes" but it also doesn't mean Nephi (by any means) is condemned. I think through this analyzation we can see the difficulty Nephi himself had with the situation, and perhaps he is in the same boat as we are in: can he explain why he killed Laban?
So, what can we learn from these passages? I hope to address this in the last part in this series of why Nephi killed Laban.