849(b) establishes when an officer can release a person who has been arrested without going before a judge or magistrate. Normally, once a person is arrested, only a magistrate can release them by setting bail or releasing them on their own recognizance. There are 3 circumstances in which an officer can do it without going to a magistrate...when the officer doesn't think there are grounds for a criminal complaint
, when the person is arrested for intoxication
only and the officer doesn't think further proceedings are required, or the person was under the influence of drugs and they were taken to a hospital for treatment and the officer thinks no further action is required.
849.5 and 851.6 deal with how that type of situation appears on your record. It basically says that if you are released by the officer and the officer does not follow up with charges, then the arrest on your record is converted to a detention. The effect of that is described as this:
"(b) In any case in which a person is arrested and released and no accusatory pleading is filed charging him with an offense, the person shall be issued a certificate by the law enforcement agency which arrested him describing the action as a detention. (d) Any reference to the action as an arrest shall be deleted from the arrest records of the arresting agency and of the Bureau of Criminal Identification and Investigation
of the Department of Justice
. Thereafter, any such record of the action shall refer to it as a detention."
So basically, it sounds like the officer got you for a minor offense and decided for whatever reason not to follow up with formal charges, so the arrest will now be listed on your record as a detention instead.