(CNN) Arkansas' efforts to execute eight death row inmates in 11 days this month has refocused attention on the death penalty.

Since peaking in 1999, executions in the US have been gradually declining amid controversy over whether lethal-injection methods are humane.

Capital punishment is still legal in 31 US states. But as the drugs needed for execution get harder to come by, states are getting creative.

Here's how we got to this point:

Opposition to the death penalty is rising ...

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