Do doping controls work?

Ricardo Ricco, confessed yesterday to taking EPO. You can read the entire article here. He, and the other three cyclists busted for doping during the Tour de France are being hailed as a sign that the new, stricter doping controls are working. Ricco sees it differently:

"During the Tour they took a lot of samples (from me), they made 10 tests in about 13 stages, two were positive and in fact in theory all the tests should have been positive therefore the method needs to be checked,"

So, does that mean that they were intentionally trying to catch him because of something that they saw from the pre-race biological passports that all 181 cyclists had to submit to before stage 1, or were they just lucky.