Our lives are to be living epistles of Christ. 2 Corinthians 3:2 We are God's witnesses because the world will not read the Bible, but they will read our lives. Let our light shine so brightly before men that when they see our good works they shall glorify our Father in Heaven. Matthew 5:16
You'll find many opportunities to testify of Our Lord Jesus Christ to inmates and jail personnel. They don't know Christ's principles, but when you speak them, the jailers will write them down on your record. They write everything down. Make sure that what they write is a Christian stand, things that Jesus would be happy to have written by the enemy.