Any driver subject to the hours of service limitations and logbook requirements of this division, who is unable to produce upon request of a representative of the department any driver’s logbook or is only able to produce an incomplete driver’s log book for the prior 24-hour period, is rebuttably presumed to be in violation of the hours of service limitations in Sections 34501 and 34501.2.
Source:
Section 34501.4, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=VEH§ionNum=34501.4..