This paper analyses the phenomenon of a shift of the burden of proof in legal persuasion dialogues. Some sample dialogues are analysed of types of situations where such a shift may occur, viz. reasoning with defeasible rules, reasoning with argumentation schemes and reasoning with mere presumptions. It is argued that whether a shift in the burden of proof occurs can itself become the subject of dispute and it is shown how a dialogue game protocol for persuasion can be extended to let it regulate persuasion dialogues about the burden of proof. It is also shown that dialogues about the burden of proof are often implicitly about the precise form of the rules used in an argument.