You pays your money you takes your choice.
If it's standing dead it's probably been there a long time and is rotten. Some woods have solid rot resistant heart wood, most don't especially the 'white woods'.
Fallen stuff is another matter, if it's not been down long it can be fine. My philosphy is, if it looks sound and it looks good for a bow pick it up and try it, you can always throw it away or burn it later. Nothing worse than thinking 'I wish I'd picked up that log'
Del