Judge Reggie Walton’s decision to admit Time reporter Matt Cooper’s notes into evidence has implications that go beyond the Libby case. Cooper’s testimony, you might recall, will be the basis for any indictment of Karl Rove, if prosecutor Patrick Fitzgerald decides to charge Rove with perjury.

The question that Fitzgerald is pondering, according to the Washington Post’s Jim VandeHei, is: “Did Rove testify falsely in February 2004 when he failed to disclose that he told Time’s Cooper about Plame’s CIA role seven months earlier?” Rove insists that he simply forgot about the conversation. Discrepancies between Rove’s recollection of the conversation and Cooper’s could make the difference in whether Fitzgerald decides to indict. Rove, for instance, argues that he forgot that he and Cooper had discussed Plame because Cooper initially called to talk about welfare reform. Cooper says he doesn’t recall talking about welfare reform with Rove.

But according to Judge Walton’s latest ruling, Cooper might not have the most reliable memory either:

However, upon reviewing [Cooper’s documents], the Court discerns a slight alteration between the several drafts of the articles, which the defense could arguably use to impeach Cooper. This slight alteration between the drafts will permit the defendant to impeach Cooper, regardless of the substance of his trial testimony, because his trial testimony cannot be consistent with both versions.

If anything, this ruling makes Karl Rove’s indictment even less likely. Unlike Libby, the sole witness against Rove is Cooper. And at this point, Cooper is not exactly looking like the guy you want to build your case around.