I read in a book that for $\beta$-decay the electrons have always been found to have an expectation value for their helicity of $h=-v/c$.

Then ist is said in the book, that it follows from this fact that such electrons are in a left-handed chiral state which is characteristic for the weak interaction.

In another article I read that the chiral state of an electron is not conserved in time. The electron will soon evolve a component with a right-handed chiral state and it will be a mixture of right- and lef-handed chiral states.

Suppose after the decay one electron moves like a free particle.
When it evolves a right-handed chiral component in addition to the left-handed component it starts off with, how can its helicity be conserved?