@DozyW
I agree with you entirely on the criminalization of accidents.
The potential problem I see with the legal investigations into accidents in some places - Italy especially comes to mind - is that there's no parallel to the English inquest process. If there's a death, then the legal investigation into the circumstances involves the same sort of prosecutors who'd eventually be involved in filing charges against suspects.
The professional accident investigation could thus potentially be hindered and disrupted. It could make it difficult to get people to testify freely, since there's a clearer lingering threat of prosecution in the process. If inquiries into the causes and facts proceed before and without relevance to potential prosecutions, then I suspect there's more chance of getting to the bottom of the circumstances, and reducing the opportunities for repeats.