Maria Stubbings, of Chelmsford in Essex, was strangled with a dog lead in 2008 by Marc Chivers, who had already killed a previous girlfriend.
Her brother Manuel Fernandez has told ITV Daybreak that the family have been calling for a public inquiry.
He said: "This highlights issues around domestic violence with one police force but it's actually a national problem."
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A grey start to the weekend with patchy rain for Scotland and eastern England.
A 31-year-old, stabbed nine times when he asked a man to stop harassing his girlfriend, has raised more than $28,000 for hospital treatment.
The Prince has called for "zero tolerance" on the ivory trade, which he says is increasing "alarmingly".