A convicted murderer, threats to kill and numerous reports of stalking and harrassment. They're all factors the police need to take into account when a victim of domestic abuse calls for help. Too often, though, police are failing to spot the warning signs until it's too late. This, despite repeated concerns voiced by its own watchdog, the Independent Police Complaints Commission and detailed guidelines and procedures on how officers should investigate domestic abuse. Every week, two women in the UK are killed by a violent partner or ex-partner. So it's crucial police can identify who is most at risk of harm and respond appropriately. John Waite investigates the cases where police officers breached their own guidelines and failed those whom they needed to protect.