KABUL — An Afghan official says the policewoman who killed an American contractor in Kabul is an Iranian who came to Afghanistan 10 years ago with her husband and obtained a fake ID through him. Interior Ministry spokesman Sediq Sediqi said Tuesday she had displayed “unstable behavior” but that the investigation revealed no militants links so far. On Monday, the policewoman identified as Sgt. Nargis shot 49-year-old Joseph Griffin, of Mansfield, Georgia, in what was the first such shooting by a woman in a spate of insider attacks by Afghans against their foreign allies. “Our investigation shows that Nargis is an Iranian national. After her marriage with an Afghan she managed to obtain an Afghan ID illegally and joined the police,” interior ministry spokesman Sediq Seddiqi told reporters in Kabul. “Our investigation also shows she was suffering from a psychological instability and our understanding from the past 24-hours investigation is that she is not associated with any armed opposition groups,” he said. The US-based security firm DynCorp International says on its website that Griffin was a US military veteran who had earlier worked with law-enforcement agencies in the United States. In Kabul, he was advising the Afghan police force. — Agencies