Necessity appears to be an affirmative defense where the defense bears the burden of proof by the preponderance under PC 2.04, but some of the cases I am reading refer to PC 9.22's language that it is a justification and the bruden is on the state to diprove the justification....Anybody got clear law on how to allocate the burden in the charge?

Read Section 9.22 in conjunction with Section 9.02. Section 9.02 creates the defense of justification. Section 9.22 defines necessity as a type of justification. Because justification is a defense under Section 9.02, you follow the dictates of Section 2.03, which basically puts the burden on the State to disprove it at trial. In other words, if a jury finds the conduct justified, or has a reasonable doubt on that issue, it acquits the defendant.

Okey doke...Thanks