If you are looking for a Bible verse for your incarcerated loved one, check this one out. (By that I mean, read it in context, preferably in more than one translation and possibly check out what others say about it. BibleGateway.com is a useful "one-stop" resource.)
As I talk with and read the writings of incarcerated individuals I see a recurring temptation: to call God a liar by embracing doubt about the truth of forgiveness for themselves. For new Christians this may be a misunderstanding that to be forgiven is to make all the consequences of their errors go away or that temptation will go away. The rush of new faith can result in a "high" that more mature Christians understand is wonderful, but not an uninterrupted state throughout our time on Earth. Like small children, we have a lifetime of growing in faith and understanding where dealing with consequences and temptations actually serve as spiritual workouts.
This verse from 1 John speaks, not to people who don't know Christ or disdain His relationship to us. This verse is addressed to those who are earnestly seeking to understand what following Christ is all about or who are active Christians who are pursuing a Christ-centric life -- both situations common for those we love who are incarcerated.
It is the essence of hope in the face of the broken human condition and allows us, when we stumble and fall, to arise in Grace to learn and move ahead in our journey of faith. This NOT an excuse to let our self-will run riot, but rather proof of the compassion of our Heavenly Father during our remaining time as we seek God's will in our daily lives.
There is inherent risk in sharing the challenges of our journey with our incarcerated loved ones since they often bash us over the head with it, but in the end, honesty can help everyone. And we do not risk the truth on our own: God is always on board for gentle truth!