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COLUMBUS, Ohio -- An anesthesiologist has testified that an Ohio inmate facing execution next week from an untried method is at substantial risk of a medical phenomenon known as air hunger.

David Waisel, a professor at Harvard Medical School, says death row inmate Dennis McGuire will experience terror during the first five minutes of his execution as a result.

Waisel testified Friday at the beginning of a two-day federal court hearing on the state's two-drug lethal injection combination. It has never been used to put someone to death in the U.S. The drugs were chosen because of a shortage of others.

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The state says its own expert can argue that experiments have shown the suffocation-like syndrome known as air hunger won't happen. They say McGuire's challenge is a last-ditch attempt to avoid execution.