I used to have to testify in civil and criminal proceedings a few times a year as part of my job. If you aren't trained to talk to police or adversarial attorneys, don't.
The magic is essentially talk to them like you would a call center agent. One topic per interaction. Use simple language. Answer a question directly. "He went that way." "I don't know."
Don't answer unasked questions. Don't demonstrate how smart you are. Don't try to "help". If you help, do an Irish goodbye asap.
At the end of the day or incident, the officer is going to write an incident report. You never want to stand out or be interesting that report. The more interesting you are, the more likely you are to get sucked in. I have a colleague who has been ordered to appear at some court in the Bronx for a traffic accident two years ago that he helped with, that turned out to be an insurance fraud case.