This is an evidentiary question best specifically posed to your lawyer in your case. Don't post any facts here, but generally yes, state of mind is an amorphous concept.
Courts are very specific in their understanding of the state of mind exception for evidence that is otherwise inadmissible. If the defendant's state of mind is not relevant, and often it isn't, then the evidence will not be admitted. If the evidence proffered on that basis doesn't tend in reason to illuminate the defendant's state of mind, then the evidence wont be admitted.
What may seem amorphous and indistinct to the person who does not deal with the concept on a daily basis may seem very clear and not the least random or meaningless to a judge who hears trial testimony and applies the evidence code to proffered evidence all day long every day.
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When a person's state of mind is relevant, then statements can be introduced not for the truth of the actual statement but to show that persons state of mind. There are many crimes that have an intent requirement. So if I person says "I am going to kill you" and then stabs that same person, you can infer that his intent was to kill the person. There are other situations where a persons state of mind is relevant and this exception would apply.