  Understanding spin physics in graphene is crucial for developing future
two-dimensional spintronic devices. Recent studies show that efficient
spin-to-charge conversions via either the inverse spin Hall effect or the
inverse Rashba-Edelstein effect can be achieved in graphene by proximity with
an adjacent spin-orbit coupling material. Lateral spin valve devices, made up
of a graphene Hall bar and ferromagnets, are best suited for such studies.
Here, we report that signals mimicking the inverse Rashba-Edelstein effect can
be measured in pristine graphene possessing negligible spin-orbit coupling,
confirming that these signals are unrelated to spin-to-charge conversion. We
identify either the anomalous Hall effect in the ferromagnet or the ordinary
Hall effect in graphene induced by stray fields as the possible sources of this
artefact. By quantitatively comparing these options with finite-element-method
simulations, we conclude the latter better explains our results. Our study
deepens the understanding of spin-to-charge conversion measurement schemes in
graphene, which should be taken into account when designing future experiments.
