The way police handled a domestic violence incident before a woman's death is to be investigated.
Terrie-Ann Jones, 33, was murdered by her ex-partner, John Lewis, at her home in Cimla, Neath Port Talbot, on 5 January.
Ms Jones's family have made a complaint over how South Wales Police dealt with an incident involving the couple in August 2017.
The Independent Office for Police Conduct (IOPC) will now investigate.
Its will also look into how the family's complaint has been handled by the force.
Regional Director Catrin Evans said: "My thoughts are with Ms Jones' family and friends at this difficult time.
"We have made contact with her family and will keep them updated on our progress.
"Our investigators will be examining the incident last August and whether South Wales Police followed local and national policies and guidance."
John Paul Lewis, 56, of Briton Ferry, was convicted of the murder of mother-of-two Terrie-Ann Jones in July. He was given a life sentence, with a minimum term of 19 years.
Ms Jones' mother, Kay Lauro, has since spoken out to urge domestic violence victims to seek help.
She said: "Even if you don't want to talk to your friends or family, there is plenty of help out there.
"I'm begging anyone who is the same situation as my Tan, whether you're a woman or a man, please speak to someone."