The first double execution to take place in the US in 16 years was carried out by Arkansas on Monday night amid a fierce dispute over whether the prisoners were subjected to a botched procedure amounting to cruel and unusual punishment.

In dramatic events that erupted a little over an hour after the first prisoner, Jack Jones, was put to death, a federal judge stepped in and temporarily stayed the lethal injection of the second, Marcel Williams, on grounds that Jones’s execution might have been unconstitutional. In frantic legal wrestling, the state conceded that it had spent some time trying to insert an IV line into Jones’s neck, but had failed in the endeavour.

The deputy solicitor general, Nicholas Bronni, admitted in a court filing that the execution team had tried “to place a central line in Jones’ neck, but the attempt was unsuccessful”.

Lawyers representing Williams instantly protested to the courts that it had taken 45 minutes for the execution team to find a vein into which they could inject the lethal cocktail into Jones. The attorneys warned that their client was obese, weighing 400 pounds, and that would render finding his veins even more difficult than his fellow death row inmate.

The double execution in Arkansas, carried out about three hours apart, marks something of a departure for the death penalty in both the state and the US. Until this month, Arkansas had not executed anyone for 12 years and nationally capital punishment has been markedly declining, with only 20 executions last year, the lowest number since 1991.

Jones, 52, was sentenced to death for the 1995 rape and killing of Mary Phillips. He strangled the bookkeeper with the cord to a coffee pot while her 11-year-old daughter, Lacey, who survived, was in the room.

Williams, 46, was sent to death row for the 1994 rape and killing of 22-year-old Stacy Errickson, whom he kidnapped from a gas station in central Arkansas. Authorities said he abducted and raped two other women before he was arrested over Errickson’s death. Williams admitted responsibility to the state parole board last month.