Tha problem with US law is that it is relevant to the State and things like the death penalty were made the govenors responsiblity. The likelihood of the 60's police carrying out such actions is highly likely, due to lack of force depth and training. The higher trained members of the force were either FBI, or CIA.
As for the coroner speaking about evidence to the detective; I think that it's all about circumstance. You have to look at the relevance to the case and sensitivity. If the evidence was out of a sealed contamination bag then it couldn't have been that sensitive as not too share it with the coroner, especially if it was relevant to the dead body and possibilties leading towards the death of the victim. The US have many laws which are generic, but even more that are indicative to each State. Sorry it's such a boring drawn out answer.