The Leggett–Rice effect in liquid 3He was proposed on the basis of Fermi liquid interactions of the 3He quasiparticles. Consideration of the interparticle interactions in polarised gaseous 3He led, similarly, to spin rotation effects describable by a Leggett–Rice equation. In spin polarised solid 3He an analogous effect has been proposed from a consideration of the inter-nuclear exchange interaction. We show, in this paper, that spin rotation behaviour of the Leggett–Rice type in all these systems may be understood as a consequence of symmetry constraints.