It still comes down to this...a LEO can not just say you are a threat to yourself in Ca. and get you a 72 hour hold. He must be able to qualify the statement with something real and tangible that will pass the smell test. If you go tinfoil hat; you may just qualify.
The cop on the street can't simply have a person admitted for a 72-hour eval. I believe the phrase I've heard is that the 5150 form only gets them to the front door; then the staff has to agree they need an evaluation. (And there has to be a bed available. Big bottleneck.)
The official formalities and what happens in real life may sound the same but are not quite as protective of your rights as you may think.
If LEO shows up with someone and says they are a threat the credible law enforcement officer will typically be believed and they will go along with thier initial assessment that the individual needs to be at least evaluated as a threat to themselves or others.
He may need to articulate a reason, but once done it is almost a certain thing.
As for 5250 you are correct that it takes a little more, I kept it simple for the sake of the thread. Even there the specific professionals that do such things on a regular basis go through the motions, make an educated determination and move on to the next guy. These are professionals that make thier rounds check forms, and deal with such things on a regular basis.
While a hearing may sound professional and give images of a court room to the average person, some guys set up in an office or available area or designated area and make a determination on various cases, then move on to thier other work. Its not like there is a criminal trial, or the burden of proof required in a criminal court with witnesses challenges to evidence, a jury, or bias towards the defendant with reasonale doubt criteria.
The way these things can remove rights is with much lesser difficulty than in a criminal court with all the rights accused get there, and bias towards the defendant. It is less likely than a 5150 and more difficult, but it also prohibits people for life federally.
In a nation that prides itself on giving rights to the criminally accused and an intended bias towards not guilty built into the system, this mental health system certainly sidesteps a large percentage of those rights and is more in line with the criminal justice system of some third world nations.
(And there has to be a bed available. Big bottleneck.)
Which is essentially saying one of the big things protecting people from excessive abuse is a lack of mental health funding for more hospitals and beds.