The Israeli soldier who shot a Palestinian attacker in the head while he lay immobilised on the ground in March has gone on trial for manslaughter.

Elor Azaria, 19, whose actions were filmed by a Hebron resident, “acted in contrast to the rules of opening fire and without any operational justification,” according to military prosecutors.

Azaria argued that Abdel Fattah al-Sharif, lying motionless on the ground, having already been checked for bombs, still posed a threat. However new footage, aired by Israel’s Channel 2, appears to contradict this claim, showing the attacker’s knife to be several metres away.

Rights groups such as B’Tselem, which published the original footage, have argued that Azaria’s actions amount to summary execution, after a coroner confirmed his shot to the head was the cause of death.

But in an unusual and potentially prejudicial step, Prime Minister Benjamin Netanyahu called the soldier’s family before the trial began, sympathising with their concern, after polls showed most Israelis think he should not be jailed. Only one in five respondents thought criticism of the soldier was justified.