LITTLE ROCK, Ark. — After nearly a dozen years without an execution, Arkansas is racing to put eight men to death next month over a 10-day period — an unprecedented timetable the state says is necessary because one of the three ingredients in the lethal injection will soon expire.If carried out, the executions beginning April 17 would make Arkansas the first state to execute that many inmates in such a short time since the death penalty was reinstated by the U.S. Supreme Court in 1976.The accelerated schedule calls for prison staff to conduct four double executions, with only a few days in between. It poses a number of risks, experts say, and the state's preparations are shrouded in secrecy.Some attorneys and anti-death penalty groups question whether the quick turnarounds will intensify pressure on the prison staff and cause problems, as happened in Oklahoma in 2014, when an inmate writhed and moaned on a gurney for 43 minutes after his injection, or in Arizona, where the fatal dose took nearly two hours to work.An investigation in Oklahoma found that intravenous lines had been connected improperly, in part because of the "extra stress" from the state's scheduling of two executions on the same day."The stress on the prison and medical staff will be increased, and the risk of making mistakes is multiplied," said Dale Baich, an assistant federal public defender who witnessed inmate Joseph Rudolph Wood's slow death in Arizona in 2014. "This along with using a drug that has been used in numerous botched executions should make the prison officials in Arkansas very nervous."At the heart of the rush is the shortage of the sedative midazolam, which is used to put an inmate to sleep before receiving the lethal chemicals.