Re: Use a net, you idiots.
Anyone standing under a prison payload of any size would be a Darwin Award Candidate, spike or no spike, simply by accounting for the idea that 5 pounds or so to the noggin (especially from a high enough altitude) can simply kill with sheer blunt force trauma.
The prisoners waiting for the drop would wisely keep clear until it lands, THEN rush for it. Plus any net-cutting implement would instantly become a panic-inducing prison weapon.