Finally, the ranch is remote and vigilante justice appears common in the area (as evidenced by George and Lennie's flight from Weed). George isn't likely to be prosecuted.

As George and Candy look down at Curley's wife in the barn stall, George reasons that the other men need to be told that she's dead. He knows that Lennie is most likely responsible and says that he will return to the bunkhouse—but he tells Candy to wait until he reaches this building and goes inside.

"Then...you come along and make like I never seen her.... So the guys won't think that I was in on it."

Candy agrees to do this. He waits for a while, then he goes up to the bunkhouse and informs the men. When the other men come into the barn, they race around the last stall; George has joined them, but he has put on his blue denim coat and has a hat pulled down over his face because he wants to avoid scrutiny. The men's attention is on Curley's wife.

As Curley looks at his wife, he calls out, "I know who done it." Slim quietly suggests to George that this scene may be "like that time in Weed...."

Slim sighed. "Well, I guess we gotta get him. Where you think he might of went?"

George stumbles some on his words, but he finally says that Lennie would have gone south because they arrived from the north. Then he urges the excited men, "Don't shoot 'im. He di'n't know what he was doin'." But Curley shouts, "He got Carlson's Luger. 'Course we'll shoot 'im." Curley desires revenge against the man who has broken his hand and now, he supposes, has killed his wife. Because he does not trust George, Curley orders him to stay behind.

However, George sneaks away. In fact, the scene is almost a repeat of his and Lennie's first night as they camped before the fire. However, this time George does not scold Lennie, nor does he object to reciting the dream. As Lennie urges George to buy their land now, George agrees, then he raises Carlson's gun, steadies it, and pulls the trigger. Lennie falls forward; George looks at the gun and hurls it away from him.

When the others arrive, George again studies his right hand, which has held the gun. Curley sees what has happened. "Right in the back of the head," he observes. "Never you mind," says Slim, who has "God-like eyes" (Ch.4) and whose "ear heard more than was said" (Ch. 2). Slim "looks through George and beyond him." He simply says, "A guy got to sometimes." Clearly, his words indicate a deeper understanding than that of the others. Slim reasons that George has shot Lennie in order to prevent his being killed painfully by Curley. Slim also realizes that even if he were put in prison, Lennie would not fare well without having George around.

With this one exception, the other men believe, as Carlson does, that Lennie had the Luger and George got it away from him and shot him.

"Yeah. Tha's how." George's voice is almost a whisper as he affirms this conjecture of Carlson's, and he still looks steadily at his right hand that has had held the gun. 

With his deeper understanding, Slim reaffirms his previous remark, "You hadda, George. I swear you hadda. Come on with me." In a gesture of protection, Slim "led George into the entrance of the trail and up toward the highway."

Slim's affirmation that George has been right in what he has done indicates that Slim would also defend George's actions as acting in self-defense, just as the others believe.

George pulled the trigger with intention to kill. He considered what he had to do (retrieve a gun, find Lennie in the exact location he knew Lennie would be in, and position Lennie to be ready to be shot). He had a good intention, but it was an intention to kill. We know this because he shot Lennie in the back of the head, told him the story of having a little place and living off the fat of the land, and he made Lennie as comfortable as he could for the moment of death. This is kind gesture, but it demonstrated to us as readers careful planning. That makes it murder.

If the charge was manslaughter, it would be on accident. There was no accident here, it was purposeful. Sometimes murder can be in the second or third degree. These are in cases of defending one's self or someone else, or being not as sane as one normally is.

I think he knew exactly what he was doing, this makes it first degree.

In Of Mice and Men, I think George performs a "mercy killing," not murder, on Lennie, his long-time friend.

To convict on murder you need: 1) the act of murder and 2) an intent to kill which is intentional, purposeful, malicious, premeditated.

So, while George's mercy killing is intentional, purposeful, and premeditated, it is not malicious.  The two men had not had a public fight; there's no signs of scuffle.  George was a type of guardian to Lennie, and his role was that of protection.

According to California State Law, George may not be guilty of murder.  There are exclusions, according to Voluntary Euthanasia Under the Law:

• Unlawful killings without malice or intent are considered manslaughter.
• Justified or accidental killings are considered homicides. Depending on the circumstances, these may or may not be considered criminal offenses.

So, I tend to think it is voluntary euthanasia, or manslaughter, or justifiable homicide and not murder, because there is no malicious motive on George's part.  He knew that Curley and the posse were out for blood, and so he performed an act of mercy on his friend to prevent the inevitable.

Strictly by the law, George is clearly guilty of murder.  He stole the gun, which clearly established what he had in mind to do when he went looking for Lennie.  So he had a premeditated plan to kill someone and he carried it out.  That is murder, possibly first degree murder.

Morally speaking, though, George did the right thing and is innocent.  Curley and his men would surely have done much worse to Lennie.  They would have killed him painfully and slowly.  George, by contrast, killed him quickly and without Lennie knowing anything about it.  So morally, George is not guilty.

Although George is guilty of pulling the trigger, he saved Lennie from dying a horrible hanging death at the hands of Curley. In one sense, George saved Lennie from an agonizing death. If George had not shot Lennie, he would have been at the mercy of Curley. Since Curley had no compassion, Lennie would have been hanged. Curley would have tortured Lennie. George is innocent because he saved Lennie from a horrible hanging death. George made sure Lennie felt no pain:

With great difficulty George fires the gun at the place where Carlson had told Candy to shoot the dog, the spot at which the creature would die feeling no pain.

When the reader considers that Curley would have tortured Lennie, it appears that George is innocent of taking Lennie's life. George saved Lennie's life from suffering at the hands of a cruel man. Because of George's compassion, Lennie is free from all worry and pain. 

If Curley had gotten to Lennie first, he would have caused Lennie to suffer unmercifully. Lennie did not deserve to die. He killed Curley's wife accidentally. Nonetheless, Curley would not have reasoned with Lennie. 

George did Lennie a favor by pulling the trigger. Lennie was already a dead man due to Curley's anger. George is not guilty of killing Lennie. George saved Lennie from hanging. George saved Lennie from Curley. Lennie dies hearing George tell about their dream. Lennie dies dreaming about his farm and farmhouse. Thanks to George, Lennie will suffer no more. 

George had no choice. He had to shoot Lennie. He is guilty of having compassion on a mentally ill man. Even Slim knows that George had no choice:

Slim, still at George’s side, says again that George only did what he had to do.