Torque,
I base my on the Louisiana State Law which I posted the Link that contains the full text of the Law.
If you read the law you will see a reference to "Violent Crimes" that can lead to charges of Manslaughter upon the death of a person as a result of any of the many crimes listed.
Specifically , section 39 in that long list has to do with fleeing from an Officer which is among the crimes the suspect was charged with in addition to the Manslaughter charge.
The information required to prefer those charges does not require the results of any accident investigation.
Yes, the Defense Counsel can raise all sorts of arguments and challenges and in time could feasibly include the results of the accident investigation or try.....during the Trial if one occurs.
The criminal investigation will define the time line and chain of events that occurred during the pursuit and that will be examined closely by the Defense Counsel of the Suspect.
The UK System is not much different in general terms I would imagine. The AAIB Investigation is separate from the Police and other authorities as evidenced by the many discussions here over the years.