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."
More top news
Andy Murray's hopes of a first French Open title remain intact after he pulled off another great escape against Radek Stepanek
Emergency services are at the scene of a "very serious" digger crash near Glasgow.
A woman who had just arrived back at Manchester Airport after a holiday abroad was surprised with a flash mob - and a wedding proposal.