Neither of those people were the lead homicide investigator who recommended Manslaughter charges. (Which, incidentally, would carry a 30-year sentence in this case since the victim was under 18.)Do you even read the things you're quoting?
"The first detective to interview Zimmerman about the shooting was a narcotics officer".
That has absolutely nothing to do with the first officer on the scene stating Zimmerman had grass on his back, and blood coming from his nose and head. Nothing.
The "interview" was conducted back at the station, probably 30-45 minutes later.