U.S. State Department said at the time it had no evidence suggesting rebels had used chemical weapons. Russia, a Syrian ally, says its investigation of a March attack in Aleppo, which apparently involved chemical weaopns, found that the charge used was homemade and similar to projectiles produced by the group Bashaar al-Nasr, part of the opposition Syrian Islamic Liberation Front. Sarin was discovered in samples from the scene, the foreign ministry said. Assad's motive unclear Some experts on the region question why al-Assad would have ordered the attack. Al Assad has no credible motivation to use these weapons at this stage, and in this phase of the conflict. He is not losing, writes Ed Husain of the Council on Foreign Relations in a CNN Opinion column. He pointed out that some suggest the al Qaeda-affiliated al-Nusra Front or other opposition elements may have carried out the attack to bait America into the conflict. William Polk, who served U.S. administrations during the Cuban Missile Crisis and and 1967 Middle East War, writes in The Atlantic, I do not see what Assad could have gained from this gas attack. Analyst: No way in hellU.S. can back up death toll Questions about the purported death toll in last month's attack also raises questions about the solidity of the information the U.S. is using. A preliminary assessment determined that 1,429 people were killed in the