So you know ... most of the testing is done with urine. Most of the time with blood.
Few times I had people at my place that was under USADA control and they only gave/collected urine.
Lot of stuff is by-passed by urine test. Lot of stuff is sophisticated synthetic blood stuff. Lot of athletes do dope. sometime are not cought.
I think is not defending because he knows he will not be able to defend it.