The LA Times reports that:

California's giant public pension fund is suing the nation's three top bond credit-rating companies for issuing "wildly inaccurate" rankings on investments that it said cost pensioners "perhaps more than $1 billion."

The California Public Employees' Retirement System on Wednesday drew plaudits and skepticism for raising legal questions about the firms' gold-plated AAA rankings for investment funds that collapsed in 2007 and 2008.

. . .

But critics wondered whether CalPERS, the nation's largest pension fund, might be trying to evade responsibility for failing to perform enough of its own diligence before sinking $1.6 billion into so-called structured investment vehicles that held mainly mortgage-backed securities.

Well, yeah.  Both are true. CalPERS is right to bust the rating agencies for the obvious half-assed job they did in recent years in judging the risk of various investments.  But yes, CalPERS is also trying to slough off blame.  They are the ones responsible for making those investment decisions.