CHP DUI Enforcement Manual, California, states:
Officers should ask a series of pre-(field sobriety) test questions.
These questions are designed to illicit (sic) information that will assist the officer in developing an opinion as to alcohol and/or drug impairment.
The questions contained on page 2 of the CHP 202, DUI Arrest-Investigation Report, may be asked without a Miranda admonition during a California DUI investigative detention.
However, if the driver is placed under arrest, California CHP DUI officers shall advise him/her of his/her Miranda rights prior to asking any questions intended to solicit incriminating statements.
[If they do not, DUI criminal defense lawyers will move to suppress those statements.]
California Drunk Driving defense attorneys have access to this excerpt and the entire DUI enforcement manual used by the California Highway Patrol.