Unsolved murders/cold case "deck of cards" in prison-how helpful?

I know some states have distributed playing cards to inmates with cold cases on them, looking for leads in return for reward money or reduced sentences.

Has this worked? If this practice were more widespread would it likely result in the ability to solve more crimes?

I ask the question because someone I went to high school with was murdered and apparently there are few leads. The case was fairly high profile. I wonder if inmates in the state prisons or local city jails have info, but no way to know this unless the cases are publicized to inmates…

According to this website and this website it seems to have some effect. At least two cases were solved already.

Do they offer these playing cards to the law abiding citizens? Maybe they can help as well since some of these cold cases don’t get that much attention.