After a series of botched executions last year, the US Supreme Court has agreed to review whether a common method of lethal injection is constitutional. If not, many states will need a new way to kill people.

Utah is already moving forward with a bill that would bring back executions by firing squad, which it allowed until 2004. There may be no “humane” way to put a prisoner to death, but if states are going to consider alternatives, they could reach back in history. Here’s a look at popular execution methods since the US was created in 1776:

The data were compiled from a database maintained by the Death Penalty Information Center and from research by M. Watt Espy and John Ortiz Smykla.

Legal scrutiny of lethal injection comes as support for the death penalty has dropped dramatically in the US. In 1994, 80% of Americans said they were in favor of executing people convicted of murder; now it’s just 63%, according to Gallup.

But the issue is increasingly polarized: Republicans have become more entrenched in their support, as the rest of the country grows more disillusioned with the practice:

Professor Austin Sarat, author of Gruesome Spectacles: Botched Executions and America’s Death Penalty, surveyed executions from 1890 to 2010. He found that roughly 3% of executions were botched over that time, but in the current era of lethal injection, the portion of botched executions has risen to 7%.

These botched executions can be grisly. The Guardian reported that during the 2014 execution of Clayton Lockett, the doctor was splattered with blood as he tried to set an intravenous line. Lockett “groaned, writhed, lifted his head and shoulders off the gurney, and said, ‘Man’.” The warden called Lockett’s execution “a bloody mess.”

America no longer hangs its condemned, nor gasses or electrocutes them. And it’s unlikely to return to those methods. For one, states now lack the expertise: Many have mothballed or destroyed their gallows, electric chairs, and gas chambers. There are also issues of appearance: Some methods carry more baggage than others, which is why a return to firing squads seems unlikely, even in Utah.