Ten incidents of possible police misconduct have been found by investigators looking into the killing of Jacqueline Oakes.
Marcus Musgrove was jailed in July 2014 for killing the 51-year-old.
A review was launched over her death, including contact she had with various agencies at the time.
The Independent Police Complaints Commission said it had issued notices to 26 serving West Midlands Police officers and seven police staff, advising them they are subject to investigation.
Notices have also been sent to an officer who has retired and to one who now works at another force.
An IPCC spokesman said its initial assessment had identified ten potential misconduct issues relating to incidents between April 2013 and January 2014.
"Our independent investigation is looking at whether the police officers and staff involved resourced, recorded and risk assessed the incidents in line with force domestic abuse policy," the spokesman said.
A domestic homicide review is also being carried out by Birmingham Community Safety Partnership.
Ms Oakes was discovered in a bedroom at Century Tower, Dollery Drive in Edgbaston, in January 2014.
The mother-of-four died from multiple blunt force injuries.
Musgrove, of Lichfield Road, Aston, aged 40 when sentenced, was told he would serve a minimum of 18 years.
At the time, West Midlands Police said he carried out the fatal attack after weeks of subjecting her to controlling and abusive behaviour.
Thirty-five members and former members of West Midlands Police are being investigated over events that led to a woman's murder in Birmingham.