An afterthought...did the lab your wife used follow a chain of custody protocol? If they did not, or the protocol they use isn't up to standards, you might have an avenue to follow in that direction as well. We all assume the labs must know what they are doing. You'd be surprised at how many simply don't follow strict protocol.
You might also consider hiring an attorney familiar with dealing with this sort of issue. The American Association of Nurse Attorneys should be able to provide you with names in your area.
The American Association of Nurse Attorneys (TAANA)
Keep us posted.
Prayers for your family.
Jack