Generally speaking, if evidence that involves some form of chemical testing is found to be in some way "tainted" as you have put it or that the chain of custody for testing has been broken (making an assumption that it could have been tainted before it was tested), then it is an argument that your attorney who is defending you in the criminal case can make.  The argument can come in a motion to supress the evidence, it can come up at trial to infer reasonable doubt, etc.  The strategics of how to use the information are left to the attorney preparing your defense.  So speak with an attorney and see what he or she says.