was daniel sickles actually temporary insane

So I have a essay due but I am just trying to get ideas. The topic I chose was to prove how Daniel Sickles was actually guilty in the murder of Phillip Barton Key II. He claimed to be temporary insane but it was obvious it was murder, I already have one idea which is to prove it was premeditated. I wanted about 1-2 more other reasons on how to prove he was not actually insane. Also, would like if you dropped ideas on how it was actually murder. I want to get creative with this essay. It would also be great if you can list the reference(s) you used. Please be clear with your explanation and make it sound like you wrote it and not straight off the internet. A paragraph for each is fine. So all I need is 1-2 reasons proving he was not insane, and 1 or 2 ideas on how it was actually murder.

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