Ivan Esack, 38, faces a life sentence, The Daily Telegraph reported. Sentencing was scheduled for Monday in Maidstone Crown Court.
Esack, who had been a detective constable in Maidstone, Kent, quit the police force in 2009 and attempted to become a sports agent. While he claimed to have good connections, the Telegraph said he had no clients.
He and his wife, Natalie, had separated. She was killed in April 2012.
"She drove me to it," Esack told police when he was arrested.
After the verdict, advocates for victims of domestic violence said Natalie Esack had reported threats and assaults to police. Her husband was not charged, apparently because she would later back down.
Sandra Horley of Refuge criticized the police response. She said officers should be trained to know that abuse victims are "frequently bullied into withdrawing statements or refusing to press charges."
"The onus is on the police to collect evidence and pursue an investigation," Horley said. "Failure to do so can mean that dangerous men are left free to kill."