A letter to a judge requesting leniency should be one to two pages, according to attorney James Abrenio on Avvo. The actual request should be reasonable and should not request an extremely large reduction in the sentence.
A request to a judge for leniency should provide a statement about the writer of the letter, including his connection to the person for whom he's requesting leniency. The letter should highlight positive qualities of the person in question, including academic achievements and community involvement. The letter should also cover anything the person has done to demonstrate remorse, Abrenio explains. A request for leniency can be typed or handwritten and should focus on humanizing the person being discussed.