"Objection! Relevance?" would be among the first words out of my mouth with every single question at trial, provided you couldn't head off his testimony before it was even offered (at trial or otherwise). From what I've read about the Clemens thing and the presiding judge, I don't know why he'd let the thing go that far afield. Perjury cases can be tried with almost ZERO background on the broader subject matter of the statement made in most cases. The subject matter is usually irrelevant to the primary issue of whether perjury was committed. If you have to get extraordinarily specific about the subject matter in order to have an opinion about whether the statement is false in the sense necessary for a perjury conviction, you probably shouldn't be prosecuting the case in most instances. The really interesting question, as somebody noted in the JSO comments, is which side put him on the witness list?