In something called a Care and Protection of Erin 443 Mass 567, 571 2005.  The court determined that a burden of proof on a petition for review and redetermination that the parent must make the initial showing of the change circumstances but then that the burden shifts back to DCF that has to prove by clear and convincing evidence that the parent is still unfit, and the child is in need of care and protection.

The idea is that the burden is never on the parent to prove that they are currently fit. If the burden is placed on the mother in a care and protection case to prove her current fitness, that is improper just to make an initial showing of changed circumstances.