Optical and near-infrared ( NIR ) observations of GRB020405 started about 1 day after the GRB and extended over \sim 70 days .
Photometry shows that the early decay is consistent with a single power law of index \alpha = 1.54 \pm 0.06 in all bands .
The late epoch light curves , sampled with HST and VLT , exhibit a plateau or slight rebrightening around 10-20 days after the GRB .
This bump can be modeled with a SN2002ap template underlying the afterglow .
Alternatively , the late-epoch data can also be fitted using a power law with index steeper ( \alpha ^ { \prime } = 1.85 \pm 0.15 ) than that of the early decay phase , in agreement with a late shell collision interpretation .
Spectroscopy indicates that the GRB is at z = 0.691 and that the host galaxy complex is angularly close to a system of at least two galaxies at z = 0.472 . R -band polarimetry shows that the afterglow is polarized , with P = 1.5 \pm 0.4 % and polarization angle \theta = 172 ^ { \circ } \pm 8 ^ { \circ } .