If Patty Ramsey wrote the note, then someone in that household killed the girl, and all other evidence is suspect.
Last I heard, if you looked real hard, you MIGHT find three handwriting experts on the planet who would testify that the handwriting WASN'T AN EXACT MATCH.
No handwriting expert has ever testified that the writing on the note and Patsy's handwriting was an EXACT match. The handwriting experts for the prosecution only stated that both handwriting samples displayed SOME of the same characteristics.