Professor Alex Stevens:

I agree with Ms Eastwood that we do not have good evidence that escalating sanctions works.

I will make a general, almost philosophical, point here that if we do not have good evidence that a punishment works, we should not be using it. Punishments are directly intended to cause harm, and we should not be causing harm to people unless we have very good evidence that there is a justification for that. In the absence of evidence that escalating punishments work or even that the punishment for possession works, we should not be doing it.