Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. Mrs Martin’s mother, Audrey Richardson, said during the hearing that perpetrators of domestic abuse are slipping through the net and the law is not “tight enough to control them”.She added: “You cannot save someone’s life by ticking boxes.”Mrs Martin’s family said in a statement following the inquest: “The family take comfort hearing today that if he was alive now he would have been charged with murder. A conclusion of unlawful killing is a satisfactory outcome from the coroner. This was a cowardly and evil act.”The police’s actions leading up to the murder were investigated by the IOPC. No action was taken against any officer, but the complaints body admitted that the “wisdom of returning the keys to Alan Martin should be looked at.”A Northumbria Police spokesperson said: “This case was referred to the IOPC as is a matter of course when there is police contact prior to a death. They carried out a full investigation and found none of the officers involved had a case to answer.”Our thoughts remain with the family of Kay Richardson who sadly lost her life in these tragic circumstances and we hope today’s inquest has helped answer questions they had about the case.” A coroner has urged the Home Secretary to review domestic abuse laws after a husband killed his estranged wife by letting himself into their property with keys the police had failed to seize.Alan Martin, 53, bludgeoned Kay Martin, 49, to death with a lump hammer and strangled her with an electric cable two weeks after being released from custody, where he had been questioned on suspicion of rape and domestic assault.Mrs Martin had suffered 12 incidents of domestic abuse in seven years at the hands of bricklayer Mr Martin and was considered by police to be at “high risk”, an inquest into her death heard.But Mr Martin was allowed to leave Northumbria Police custody on September 7 last year with his set of house keys.Just before 8pm on September 20 he let himself into their formerly shared home in Humbledon, Tyne and Wear, and killed his wife before hanging himself.The tragedy has prompted Sunderland Coroner Derek Winter to write to Home Secretary Priti Patel to call for greater protection for domestic violence victims when their attackers are released under investigation by police.Mr Martin, who had moved into a rented property two miles away from the marital home, had defied both a restraining order and a non-molestation order when he carried out the “cowardly and evil” murder. But the coroner suggested that if he had been released on bail, with further restrictions in place, this could have prevented him from attacking his wife.Detective Sergeant Katie Smith told the inquest that it was not deemed “proportionate” to release Mr Martin on bail.The inquest heard that police had failed to apply for a Domestic Violence Protection Order, which puts protective measures in place when there is insufficient evidence to charge a perpetrator.Ruling that Mrs Martin was unlawfully killed by her husband, Mr Winter said: “It seems to me that on occasions, particularly where there are welfare protection issues for victims of domestic abuse, that there may be a gap in her – or his – protection.”It may not have mattered in terms of Kay’s protection if Alan Martin’s keys had been removed, but some review of the procedure should take place in terms of what powers the police should be able to exercise pending matters being resolved finally in the family court or the criminal court, and that gap is a matter of concern to me.”The coroner said he would write to the Home Secretary, the police, the Independent Office for Police Conduct (IOPC) and the local authority with his concerns.