Criminal Law Questions? Ask a Criminal Lawyer.
Section 5150 is a section of the California Welfare and Institutions Code and is neither a misdemeanor nor felony. it is a civil procedure only where one can be confined for observation for at least 72 hours, if thought to be a danger to self or others
you can use this link to read the Code
a 5150 is a part of a medical record and should not appear on a background check. however, if you allow someone to have access to you medical records it could be revealed.