I was exploring the Castle Dungeons in Solitude, I came across with this "evidence chest." there are lots of foods,books, armors, weapons and stuff in it. also there is a blonde woman in one of the cells, but I can't unlock the door or talk to her. it seems she is a part of a quest, I wonder if this chest has her stuff in it? would that quest be affected if I steal from this chest now?

I think the stuff in the evidence chest is the stuff you had stolen. You can steal it and I don't think she is part of a quest, just a random in prison type thing. but that is the stuff you had stolen before XD

Here is the thing: You steal stuff and go to jail it gets put into the evidence chest there which is why you usually don't get it back but there is one place where going to jail lets you keep everything (damn Winterhold)