A pathologist hired by death row inmates' attorneys says a South Carolina man executed by firing squad was conscious and likely in extreme pain for up to a minute.

Two House members asked the governor, prisons director and top legislators to investigate whether Mikal Mahdi's execution in April followed protocol.

Mikal Mahdi was the second man in South Carolina to be executed by a three-person firing squad on April 11, after admitting to killing an off-duty police officer in 2004.