If the person you are witnessing to is very scientific or Jewish, I would recommend these websites.  www.shroudstory.com or www.shroud.com.  The Discovery Channel does not always have accurate information, but their most recent program is excellent.  I think it is entitled "Unraveling the Shroud".
 
I believe that God in his mercy has provided some physical evidence for this generation, just as he did for doubting Thomas.  The more I study the complexity Shroud of Turin, the more convinced I am that it could not have been made by human hands.  The image is most probably Christ's "photograph"  at the time of the resurrection.