Here is a potentially relevant story that appeared in Nature (premier British science journal) in 2002 that could possibly explain Tyler's predicament:

http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v417/n6884/full/417010a_fs.html

The premise is that there are people who are "blood chimeras" - that is they have their "own" blood plus apparently the blood of someone else, most often a twin or a twin that was spontaneously aborted during pregnancy. This leads to an individual who may be carrying blood cells with two different sets of blood group markers - this is the basis of the test that nailed Tyler. So, is it possible that Tyler is one of these "blood chimeras"? There should be a simple way to determine this. They should be able to separate the blood cells that are "different" is what is called a FACS machine (Fluorescence Activated Cell Sorter). So, you isolate these cells then do a series of standard forensic type DNA tests. Is the DNA in the "different", apparently foreign, cells from a close relative of Tyler (i.e., an unknown spontaneously aborted twin; I assume he doesn't have a living twin, but I don't know this), or is it truly from an unrelated individual. If it's from an unrelated individual the situation would be grim for Tyler, but the case still would not be closed, because it is possible that in a long-ago transfusion (has he ever had one?), presumably during surgery, perhaps he was "seeded" with stem cells from the donor cells, resulting in persistance of foreign blood cells. I am a scientist, speaking somewhat outside my field, but it seems that, happily, the technology is available to sort this out

We can all only hope that something like that turns out to be the explanation. I really like Tyler. He's a great rider to watch, he is getting old, but I hope he really is clean..

Here is a potentially relevant story that appeared in Nature (premier British science journal) in 2002 that could possibly explain Tyler's predicament:

http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v417/n6884/full/417010a_fs.html

The premise is that there are people who are "blood chimeras" - that is they have their "own" blood plus apparently the blood of someone else, most often a twin or a twin that was spontaneously aborted during pregnancy. This leads to an individual who may be carrying blood cells with two different sets of blood group markers - this is the basis of the test that nailed Tyler. So, is it possible that Tyler is one of these "blood chimeras"? There should be a simple way to determine this. They should be able to separate the blood cells that are "different" is what is called a FACS machine (Fluorescence Activated Cell Sorter). So, you isolate these cells then do a series of standard forensic type DNA tests. Is the DNA in the "different", apparently foreign, cells from a close relative of Tyler (i.e., an unknown spontaneously aborted twin; I assume he doesn't have a living twin, but I don't know this), or is it truly from an unrelated individual. If it's from an unrelated individual the situation would be grim for Tyler, but the case still would not be closed, because it is possible that in a long-ago transfusion (has he ever had one?), presumably during surgery, perhaps he was "seeded" with stem cells from the donor cells, resulting in persistance of foreign blood cells. I am a scientist, speaking somewhat outside my field, but it seems that, happily, the technology is available to sort this out

Cool reference; thanks for schooling me. However, it's not really applicable in hind sight. If it's not agreed to before competition, you can't scavange the literature to establish ground rules after the fact.

His goose is cooked within the boundaries of the rules as of the start of the Olympics. Since they failed to get conclusive results from the olympic "B" sample, he's exhonerated. Since his Vuelta "B" sample failed, he's toast.

I agree, adequate testing should be in place before adopting standards. Maybe the riders can form a union similar to the NFL player's association and agree to standards in contracts? Keeps unscrupulous labor relations down in that sport.