The report that the defense does have indicates no tox screen was done, so it's not a matter of Nifong holding back. It's a matter of Mangum holding back at the time.
Do you think they really didn't do a tox screen or is there just not one in the file Nifong gave to Osbon?
This is a separate thread that says the box was checked that no tox test was done.
http://freerepublic.com/focus/f-news/1636545/posts