It is mostly told in a letter which the state itself introduced in this case....
They lived close together, only a few blocks from each other; saw each other every day; but Leopold wrote him this letter:
October 9, 1923.
Now, as to the third, last,
and most important question. When you came to my home this afternoon I
expected either to break friendship with you or attempt to kill you unless
you told me why you acted as you did yesterday....
Now, Dick, I am going to make a request to which I have perhaps no right, and yet which I dare to make also for "Auld Lang Syne." Will you, if not too inconvenient, let me know your answer (before I leave tomorrow) on the last count? This, to which I have no right, would greatly help my peace of mind in the next few days when it is most necessary to me. You can if you will merely call up my home before 12 noon and leave a message saying, "Dick says yes," if you wish our relations to continue as before, and "Dick says no," if not.
It is unnecessary to add that your decision will of course have no effect on my keeping to myself our confidences of the past, and that I regret the whole affair more than I can say.
Hoping not to have caused you too much trouble in reading this, I am (for the present), as ever
Now, I undertake to say that under any interpretation of this case, taking into account all the things your Honor knows, that have not been made public, or leaving them out, nobody can interpret that letter excepting on the theory of a diseased mind, and with it goes this strange document which was referred to in the letter.
"I, Nathan F. Leopold, Jr., being under no duress or compulsion, do hereby affirm and declare that on this, the 9th day of October, 1923, I for reasons of my own locked the door of the room in which I was with one Richard A. Loeb, with the intent of blocking his only feasible mode of egress, and that I further indicated my intention of applying physical force upon the person of the said Richard A. Loeb if necessary to carry out my design, to-wit, to block his only feasible "mode of egress."
There is nothing in this case, whether heard alone by the court or heard in public that can explain these documents, on the theory that the defendants were normal human beings.