Of Mice and Men:
Imagine that George is arrested and has to explain what happened to the lawyer. Use the first person to write a statement explaining the relationship between George and Lennie and motivations for killing Lennie. (affective George tone)
If this is coming from George's perspective, his best explanation to a lawyer would be to simply tell the truth. He decided to kill Lennie to avoid any mishaps in the future. Also, for Lennie's sake, George would rather kill Lennie himself, as difficult as it was, rather than let Lennie be killed by Curley or sit in a jail cell and go through a trial. Remember that Candy regretted not killing his old dog himself. Candy mentions this to George in Chapter Three:
I ought to of shot that dog myself, George. I shouldn't ought to of let no stranger shoot my dog.
This is a parallel to George being responsible for Lennie. George is Lennie's responsibility; therefore, George would own up to that in discussion with the lawyer. George might say something like this, but this is not written in George's affective tone:
"Lennie had the strength of an ox but the mind of a child. He became my responsibility years ago. I did my best to watch out for him but I couldn't keep an eye on him all of the time. When he managed to hurt someone again, I decided to kill him rather than let something like this happen again. I also didn't want Curley to get his hands on Lennie and worst of all, I didn't want Lennie to have to sit in a jail cell. He did kill that girl but only because he panics and doesn't know his own power: strength of an ox, mind of a child."
(You should play with the tone to get George's characterizations of speech. He uses slang like the rest of the ranchers. Look at some of George's lines to get an idea.) Here is a line by George at the end of Chapter Three after the fight between Lennie and Curley:
George broke in, "Lennie was jus' scair't," he explained. "He didn't know what to do. I told you nobody ought never to fight him."
Note the use of "ought" and realistic speech: "jus'" and "scair't." Consider writing George's explanation to the lawyer in your own voice and then change it to sound more like George. For example, "Lennie had the strength of an ox but the mind of a child" could be changed to "Lennie was strong as a damn ox but the poor bastard got kicked in the head and has been like a scair't little kid ever since."