Body temperature has nothing to do with whether the TouchID works or not. It has to do with other factors including blood flow and body electrical capacitance when changes drastically at death. But the most important is the fluids still being in the fatty pads under the finger tips which are maintained by blood pressure. They'd have to catch it quite quickly for it still to work. These days, disturbing the body in situ at the death scene is not permitted until CSI is finished with it. Also, I've heard no evidence they'd found his iPhone yet. He may have left it at home.
Besides, it still takes a court order to "search" his iPhone.
Agree in most cases BUT I think the events warrant the collection of evidence immediately without a search warrant due his death and the degree of his crime.... such collection may be inadmissible later but speed is of the essence in such cases “per my experience” with acts of terror. Courts can determine after the fact legality .......