* Soldier who fired didn't see protester - army probe
* Family rejects ruling, rights group warns of impunity
By Dan Williams
JERUSALEM, Dec 6 (Reuters) - Israel's army has exonerated a soldier in the 2011 killing of a Palestinian protester with a rifle-fired tear gas canister, and an Israeli human rights group criticised the ruling as a sign of military impunity.
Mustafa Tamimi, 28, was struck in the head by the canister while chasing an army jeep during a stone-throwing demonstration in the Israeli-occupied West Bank. Media photographs showed one of the jeep's rear doors slightly ajar with smoke coming out of it as Tamimi collapsed on the road.
The death deepened bitterness among Palestinians who, after years of armed conflict, say their less violent struggle for statehood still meets excessive, sometimes lethal, Israeli force.
In a statement late on Thursday, the army said an internal investigation had found that the soldier who shot the canister "did not see any people in the line of fire" and that therefore none of the soldiers involved were criminally liable.
The inquiry was impeded, the army said, by the refusal of one of Tamimi's fellow protesters - whom it did not name - to testify, and by "violent riots" at the scene as investigators tried to carry out forensic work.
The army's account was rejected by Tamimi's brother Louai, who said he had not been approached by investigators despite having witnessed the Dec. 9, 2011 shooting.
Louai Tamimi told Reuters that he had been standing next to Mustafa, throwing rocks, "4 or 5 metres (yards) or less" from the jeep.
"When the soldier shot the tear gas, there is no doubt that he saw us, and struck my brother directly," he said on Friday.
The human rights group B'Tselem said the army's account clashed with its own military regulations for firing tear gas in a manner meant to ensure it did not pose a lethal risk.
The investigators "did not explain how the firing of a tear-gas canister from the back of a moving vehicle, towards the road, under conditions that made it impossible to ensure it would not hit a person, could be deemed legal", B'Tselem said.
In a statement, it criticised the duration and limited scope of the military investigation. "Under such circumstances, it is only a matter of time before yet another unarmed Palestinian civilian is killed in this way. For Palestinians in the West Bank, the decision is a clear message that they cannot expect justice from Israel's legal system."
Army spokesman Lieutenant-Colonel Peter Lerner said troops "operated within the realm of their responsibility" against Tamimi, who had been throwing rocks as he ran at the jeep.
"Tamimi put himself at unnecessary risk, unfortunately resulting in his death," Lerner said. (Writing by Dan Williams; Editing by Mark Heinrich)