I agree with Attorney Leibowitz. I have had instances where letters were sent to the sentencing judge before court and the judge forwarded copies of it to me (defense counsel) as well as to the prosecuting attorney.
It may be better for you to have a chat with the prosecuting attorney. This way your thoughts will be known, but you won't have a paper trial leading back to you. I have heard of retribution in cases in which the recently convicted had family/friends pay the complaining witness or victim a visit. I cannot say that this will happen to you, but if you have a concern for retaliation, then may be you should not write anything. If you still have questions, contact the prosecutor who handled the case.
The answer(s) given a merely a suggestion. In no way do these answer(s) create an attorney-client agreement or any other agreement for legal representation. For legal representation, please contact an attorney in your area.
Typically, any letter written to a judge regarding a case is part of the public record. Such letters may even go into the Court file. This is to protect the integrity of the process. We don't want people to be having private conversations with judges to try to influence their opinions on cases.
If you don't want people to know what you write, you could send the letter anonymously. However, the judge likely won't give it much weight unless someone is willing to put their name behind the words. Again this is to avoid dishonest manipuations of the process.
In a criminal matter a Judge is not allowed to review anything that the State and the Defense have not reviewed first. All mail and phone calls are intercepted by their staff. The Judge is not allowed to speak with the Defense attorney unless the State's Attorney is present. The Judge is not allowed to speak to the State's Attorney unless the Defense Attorney is present. No one may speak with the Judge while a case is pending. THat would be an "Ex-Parte" communication.
For example, what if the victim wrote, Dear Judge, I never told anyone this is my life but my father (the Defendant) also raped me, he did not just beat me, I was just too scared to say it out loud. Please put him a way for life, I am begging you.
The Judge could not be impartial any longer and he would have to call a mistrial and the whole trial was for nothing and would have to be redone. Make sense? Short answer--YES, the criminal would know every word you wrote and deserves to know by that little thing known as THE CONSTITUTION.