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Scattering polarization tends to dominate the linear polarization signals ofthe Ca II 8542 A line in weakly magnetized areas ($B \lesssim 100$ G),especially when the observing geometry is close to the limb. In this paper weevaluate the degree of applicability of existing non-LTE spectral lineinversion codes (which assume that the spectral line polarization is due to theZeeman effect only) at inferring the magnetic field vector and, particularly,its transverse component. To this end, we use the inversion code STiC toextract the strength and orientation of the magnetic field from syntheticspectropolarimetric data generated with the Hanle-RT code. The latter accountsfor the generation of polarization through scattering processes as well as thejoint actions of the Hanle and the Zeeman effects. We find that, when thetransverse component of the field is stronger than $\sim$80 G, the inversioncode is able to retrieve accurate estimates of the transverse field strength aswell as its azimuth in the plane of the sky. Below this threshold, thescattering polarization signatures become the major contributors to the linearpolarization signals and often mislead the inversion code into severely over-or under-estimating the field strength. Since the line-of-sight component ofthe field is derived from the circular polarization signal, which is notaffected by atomic alignment, the corresponding inferences are always good.

On the (mis)interpretation of the scattering polarization signatures in the Ca II 8542 A line through spectral line inversions