To write a letter to a judge, first make sure that your letter is short, legible and simple. Include your full name and the reason for your letter early in the document. Learn more here: http://justicewomen.com/tips_write.html.
To write a letter to a judge, especially a letter of support, you will need to include information regarding who you are and your relationship with the accused person. Learn more here: http://www.brodenmickelsen.com/mb10.html.