These two documents are closely linked. They lay out the actual legislation and interpretations adopted by most states. Since most of my work is in Virginia and these documents apply here, you may want to check out whether these apply in your state, or not.
Also, just in case you can't find the Third Restatement, try looking for Restatement of Trusts 3d: Prudent Investor Rule.
Both pieces generally impose "the obligation of prudence in the conduct of investment functions." The person overseeing investments considers "the purposes, terms, distribution requirements and other circumstances" of the investments. Further, the investment activities must be viewed not in isolation, but in the context of the whole responding to the goals and objectives of the investment policy.
The heart of these documents is the list of parameters a fiduciary should consider when overseeing investments. This list includes general economic conditions, inflation/deflation, tax consequences, the overall components of the investment pie, other resources, needs for liquidity, and more.
Next time, we'll discuss the role of loyalty, diversification, impartiality, investment costs, and delegation for a fiduciary in the light of the UPIA and the Third Restatement.