First Witness: Jo

The first witness is Jo. Oh how I've missed her. She's not looking too good, being dead and all. But we get treated to some nice flashbacks of Jo and Dean's prior interactions. She may well be his greatest guilt, since she wouldn't have taken up hunting as strongly as she did if it weren't for Dean. And she wouldn't be dead now either, at least not at the hands of Hellhounds and a bomb blast.