An accident, by itself, is not probable cause. If you were arrested for DUI then, by law, you gave "implied consent" for a breathalyzer. Vehicle Code 23612. You are not supposed to be arrested without probable cause. Terry v. Ohio, (1968) 392 U.S. 1, 21. If you were not arrested, but gave a breathalyzer anyway, you did so voluntarily.

No, but if the officer thinks alcohol was involved in your driving and accident he/she is permitted to investigate the crime and that investigation can include a breath test in the field.

The accident may not be by itself enough but Vehicle Code 40300.5 permits an officer to arrest without a warrant and not personally witnessing the event if he has reasonable suspicion you were driving under the influence.

Many DUI suspects either admit driving or are seen by a witness which establishes driving. If then the officer has reason to suspect alcohol consumption or intoxication she may detain for further investigation and arrest. Many times the officer smells alcohol on the suspect and notices other symptoms of impairment when combined with driving give probable cause to arrest for DUI.

the accident just gave the police a reason to be there........THEN when they smell alcohol, see a bag of drugs or a lifeless body in the car they can investigate.

i assume the police report will show the smell of alcohol, poor coordination, red eyes, slurred speech etc.

if so they would ask for field sobriety test and breath or blood test.

so chances are they were right.