how to apply the M'Naghten rules in a defense of insanity?

I had just watched the pbs program on "A Crime of Insanity" which talked about the Ralph Tortorici case. I read some stuff on the information section of the page and it mentioned the M'Naghten rules. I was interested so I did some research and found this site: Insanity Lecture Notes - Help With Your Law Essay and Law Dissertation - Law Resources and Custom Essays

From the site, the rules include things like Defect of Reason, Disease of the Mind, Delusions etc.. But they all seem very very similar to me, so I'm wondering how you would apply the rules to a case - for example the Tortorici case. That is, would you apply the rules and include everything (all rules - defect of reason, disease of the mind etc) or would you just apply a few that are relevant? And if you do apply a selected few, how would you do that (like how would you differentiate between them)?

Im just kind of confused about the rules and it would really help if I could get some clarification on this issue.

Thanks in advance : )