There have been several recent incidents of electric shocks through contact with the metallic panels and frames of some solar PV systems due to electrical leakage. These incidents have also had the potential to cause a fall from height if the roof itself is conductive.
The leakage, caused by the capacitance (ability to store an electrical charge) between the solar panels and dirt and water on the panels or the roof, generally increases when the solar panels are wet.
In some situations the leakage may cause an electrical potential (voltage) on the solar PV frames, the array mounting frames and any conductive materials (e.g. metallic roofing material). While these voltages may not produce a fatal electric shock, in higher risk environments such as working at heights, the reaction to a mild shock may increase the risk of a fall.
via Solar PV systems leakage a danger at heights – Department of Justice and Attorney-General.