I believe prisons are whited fields ready for harvest because such restricted living can give way to self-examination and an interest in learning a different way to live. This is born out by the statistics: recidivism rates are lower for folks who are introduced to the teachings of Christ, supported when they express an interest in growing in faith and welcomed into the fellowship of churches who believe in redemption, reconciliation and reclamation when they return to the free world.
If your child is in prison, encourage a hopeful attitude--hope that he can use the time well, hope that she can think seriously about God and develop a relationship with God, hope that he can still live a life of purpose because all that can and does happen in any time and in any place. This is true for you too.
Be a beacon of life into your loved ones life by living well, trusting God radically, loving God passionately and sharing the changes in your life as you grow in grace.
It is the most effective sermon you will ever preach.