It's permissible for a witness to speak of his own state of mind.
That's not state of mind testimony. For example, "I was angry," "I was sad," "I felt humiliated," all refer to the witnesses' state of mind. "The defendant acted suspisciouly" is nothing more than a speculative conclusion based upon other facts. The witness should testify as to what he or she observed and let the prosecutor argue to the jury that the defendant's conduct was suspiscious.