When in prison, most of the people start to express they're life experience through tattoos. It's like a story of the upsides and downsides of they're lives. It's like a memorial, which let's you move on with your life. Once you have the tattoo, part of your life is printed on your body, letting your mind to be free. To sum up, it is the way of your expression, since there is no one that can hear you out.