nly a fraction of criminal cases involve biological evidence that can be subjected to DNA testing, and even when such evidence exists, it is often lost or destroyed after a conviction. Since they don’t have access to a definitive test like DNA, many wrongfully convicted people have a slim chance of ever proving their innocence. - See more at: http://www.innocenceproject.org/causes-wrongful-conviction#sthash.fWprieCz.dpuf