  SW Sextantis systems are nova-like cataclysmic variables that have unusual
spectroscopic properties, which are thought to be caused by an accretion
geometry having part of the mass flux trajectory out of the orbital plane.
Accretion onto a magnetic white dwarf is one of the proposed scenarios for
these systems. To verify this possibility, we analysed photometric and
polarimetric time-series data for a sample of six SW Sex stars. We report
possible modulated circular polarization in BO Cet, SW Sex, and UU Aqr with
periods of 11.1, 41.2 and 25.7 min, respectively, and less significant
periodicities for V380 Oph at 22 min and V442 Oph at 19.4 min. We confirm
previous results that LS Peg shows variable circular polarization. However, we
determine a period of 18.8 min, which is different from the earlier reported
value. We interpret these periods as the spin periods of the white dwarfs. Our
polarimetric results indicate that 15% of the SW Sex systems have direct
evidence of magnetic accretion. We also discuss SW Sex objects within the
perspective of being magnetic systems, considering the latest findings about
cataclysmic variables demography, formation and evolution.
