how can they prove the letter was written by the suspect, he left a call back # but it's not in service nemore

Question

i was left a note on my car which i believe to be a threat
it was in the regard of my family and the person left a phone number....but it is no longer in service. i have a strong feeling that it is a co-defendant in a case that i am involved in.
i tried to do the reverse look-up but go no- where.
how can the court prove it was left by the defendant....?

Answer 1

Fingerprints could have been taken, if any, off the note.
Also, Handwriting comparisions could be used.
Did you keep the note? Given it to your attorney?
Your attorney is the one that should be advising you.