Mobile phone footage circulating on social media shows police at the scene did not save the 27-year-old woman, Farkhunda, who was beaten with sticks and set on fire by a crowd of men in central Kabul in broad daylight on Thursday.
"Last night I went through all documents and evidence once again, but I couldn’t find any evidence to say Farkhunda burnt the Holy Koran," General Mohammad Zahir told reporters at her funeral on Sunday. "Farkhunda was totally innocent."
The top criminal investigator promised to punish all those involved and said 13 people, including eight police officers, had already been arrested.
The killing was condemned by the Afghan president and other officials, but also drew praise from some quarters, including from a prominent cleric, who asserted the men had a right to defend their Muslim beliefs at all costs.
Farkhunda was a teacher of Islamic studies, according to her brother, who denied media reports that she had been mentally ill. He said this was a made-up defense by their father, who wanted to protect the family after police told them to leave the city for their own safety.
"My father was frightened and made the false statement to calm people down," said Najibullah, who is changing his second name to Farkhunda in memory of his sister.
Hundreds of people attended her funeral on Sunday chanting "we want justice" and her coffin was carried by women.
The United States and other countries have spent millions of dollars in Afghanistan on promoting the rule of law, justice and women's rights since the Taliban were ousted in 2001.
Under the strict Islamist rule of the Taliban, women could neither attend school nor were they allowed to work, and were forbidden from leaving the house without a male guardian.
The last decade has seen much progress: Millions of girls now attend school and women can enter employment, particularly in major cities. But in some rural areas, little has changed and hardwon rights are at risk of being reversed as aid and foreign troops are withdrawn.
(Reuters)(Writing by Jessica Donati; Editing by Raissa Kasolowsky)
