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[SoCalDep]

I think there is confusion as to the circumstances of the incident...Is the hit and run driver (suspect) in the hospital? You stated that the "driver of the car that was hit" has massive head injuries and is in critical condition... I assume this is NOT the suspect, but an occupant of the car that the suspect hit?

As for reasons he wasn't arrested, those have been covered well in previous posts, but if the suspect hit another person and caused significant injuries then ran, that is a felony.

[P5Ret]

There is also the very real possibility that no one can ID the driver of the suspect vehicle. Making it harder on the investigating agency, not impossible but harder to prove who was driving. Quite a few deputy da's I worked with wanted more than an ID of the car, with a solo driver even if found within minutes of the collision. Oh we could arrest, but for them to take it to trial they wanted an air tight case, with an ID on the driver, or a solid confession.