As the US Supreme Court prepares to hear evidence on botched executions in Oklahoma, the Pew Research Centre has released revealing new statistics on opinions about the death penalty in the US. 

The study, which compared current views on the death penalty to studies conducted in previous decades, found that support for the practice has dropped dramatically over the past twenty years. Researchers found that 56% of Americans are currently in favour of the death penalty, compared to 78% in 1996. In the past four years alone, the share supporting the death penalty has declined six percentage points (from 62% in 2011).

Much of the decline in support over the past two decades has come among Democrat voters. Currently, just 40% of Democrats favour the death penalty, while 56% are opposed. In 1996, Democrats favoured capital punishment by a wide margin (71% to 25%).

The study, conducted Mar. 25-29 among 1,500 adults in the US, found that the majority of Americans are concerned about the possibility that an innocent person could be executed; a majority also believe that minorities are more likely than whites to be sentenced to death.

The results echo the sentiments of US Attorney General Eric H. Holder Jr., who opposes the death penalty due to the risk of someone being executed in error.