Actually no, Palmeiro getting caught doesn't necessarily vindicate Canseco, in fact, Canseco ain't helping his cause by saying he thinks Palmeiro is now clean, and his failing the drug test was rigged by MLB.
What Canseco claimed was Palmeiro was doing steroids when they were teammates; Canseco, for the most part, doesn't claim to know about the time, or people, when he didn't play/whom he didn't play with.
Therefore, theoretically, Palmeiro could've been clean through his testimony on da hill, never touched the stuff prior to that, and then started using the period afterward, the period to which Canseco doesn't think Palmeiro did anything...all in the past or something like that - but of course, he doesn't know.
Take what what you will, but I'm guessing in a court of law, they would have to dissect every piece of the claims. Basically chronologically, as it is, it's at different times.
Ha, the title's fixed!