I think since the early roman kingdom days, murders within a family (parricide) were punished by the state, at least some of them (e.g. a father might have had

I think since the early roman kingdom days, murders within a family (parricide) were punished by the state, at least some of them (e.g. a father might have had right of death over his offspring, but maybe that ended once they reached adulthood?). https://en.wikipedia.org/wiki/Poena_cullei https://en.wikipedia.org/wiki/Poena_cullei on the punishment for parricide at a later time has something on it. Eventually it would be extended to homicide outside one's family (Lex Cornelia de sicariis et veneficis), but as the GP says the article confuses things a bit between the state not being involved at all, and a lack of investigation. I think murder was just like anything else in that regard, meaning that the state would not prosecute any crimes on its own without someone going to court in the first place. But that was also the case for the jewellery example, or anything else: if nobody complained about it, the state did not have a police force looking out for these things and the crime would go unpunished.