The Supreme Court, in a 5-4 decision, just allowed Oklahoma to keep using its experimental lethal-injection drugs even though they could be leading to an extremely painful death. Justice Sonia Sotomayor, who wrote the dissent in the case for the court's liberal justices, thinks that this is what the decision amounts to:
[I]t leaves petitioners exposed to what may well be the chemical equivalent of being burned at the stake.
The conservative justices, led by Justice Samuel Alito, found that there was enough evidence that the drugs were safe to let the executions go forward. Sotomayor and the liberals, on the other hand, maintain that there's a scientific consensus that the drugs Oklahoma uses can't reliably knock someone out before killing him.
The conservatives also found that if the Oklahoma prisoners were so worried about the drugs the state is using, it was their job to come up with a safer method. That's impossible, or nearly impossible, since the reason Oklahoma and other states have been experimenting with lethal-injection drugs is that activists have successfully pressured drug companies to stop making the drugs that have traditionally been used to sedate prisoners before execution.
So the result of the Court's decision is that, because the safer options for lethal injection have been eliminated, prisoners will have to be subjected to the riskier options.