Saba
You raise a really important issue about when we need research to understand the science and when we already know the answer and we just need effective advocacy. Sometimes of course scientific findings can motivate political change, but often, the motivations for political change come from other realms. So, at this point, for the 3 strikes laws, do we need more research on their health effects or do we simply need effective political advocacy to change the policy?
This is not my area of research, but there seems to be a building consensus that 3 strikes laws were disastrous, for reasons unrelated to health. That said, there are a lot of uncertain areas related to the health effects of incarceration overall. Just showing that people who are or have been incarcerated have worse health does not mean that incarceration harms health - very possibly people who already had health risks are more likely to become incarcerated. So, how do we establish which causes the other? Your idea of a longitudinal study is a good start. The point of evaluating spillover effects of incarceration of family or community members is also critical.
maria