It's been 130 years since the Supreme Court has heard direct arguments about the method of execution -- back then, it was the firing squad. Today, it'll be on a Kentucky case; Kentucky, like California and 35 other states, uses lethal injection.

In December 2006, a California judge found that, the LA Times reports,

There was "more than adequate" evidence that the state was violating the U.S. Constitution after hearing testimony that lethal injection procedures were performed in a dark, cramped room by men and women who knew little about the drugs they administered.

The 3-drug lethal injection cocktail used by the states was rejected by veterinarians years ago as being too potentially painful. For a complete overview of the case coming before the Supreme Court, you can't do better than Nina Totenberg's NPR report.

California doctors have balked at having to participate in inmate executions. There are currently 642 men and 15 women on California's Death Row.

Photo of California's death chamber from the Department of Corrections website. A new chamber was under construction last year.