I think these are just slightly different approaches to the same goals of carceral malfeasance. You don't need to try someone more than once if you can torture a confession out of them. You don't need to torture a confession out of someone if you can try them as many times as you want.

Cops and prosecutors will use the tools available to them, the specifics of the tools varying a lot by local history and governance traditions.

Italy does have protection from repeated prosecution as a fundamental right (not least due to the directly binding charter of Fundamental Rights of the European Union).

And as the US population currently finds out, what's written in a constitution is not worth much when there is inadequate rule of law (and the US constitution offers comparatively few protections as is).