Police missed several opportunities to carry out background checks on a woman who made a series of 999 calls saying she was dangerous shortly before she stabbed two strangers in the street, murdering one of them, the police watchdog has found. Checks would have revealed the woman had previously killed her mother.

Nicola Edgington was jailed for life at the Old Bailey on Monday with a minimum term of 37 years for the murder of Sally Hodkin, 58, and given a concurrent sentence of life with a minimum term of 20 years for the attempted murder of Kerry Clark, 22.

Metropolitan police officers dealing with Edgington, who was found guilty last month, should have checked her details in the police national computer (PNC), a report by the Independent Police Complaints Commission (IPCC) found.

The same was true of staff at the police operations centre who took calls from Edgington during which she spoke of being a dangerous schizophrenic person who was likely to kill, the report said.

Had they made the checks police would have learned that Edgington, 32, killed her mother in 2005 by stabbing her nine times. She pleading guilty to manslaughter on the grounds of diminished responsibility and was deemed well enough to be treated in the community in 2009.

Edgington's condition began to deteriorate during 2011, and on the day of the attacks, 10 October, police took her voluntarily to a hospital in the early hours from a minicab office, where she was in an agitated state. At Queen Elizabeth hospital in Woolwich, south-east London, Edgington made a series of 999 calls in which she warned she could kill someone, before leaving the hospital. The record of one of the calls read: "Caller stating she is a dangerous schizophrenic and if police do not arrive on scene asap she is going to harm somebody."

From the hospital Edgington went to Bexleyheath, where she bought a knife from an Asda shop and attacked Clark, who fought her off. Edgington then stole a 12-inch steak knife from a butcher's shop before stabbing Hodkin to death.

The IPCC report concluded that while no officers had breached conduct rules, the officers who took Edgington to hospital had enough details to make a PNC check but did not do so.

It said: "In view of the nature of the incident the officers were dealing with, it is concluded that they should have carried out a PNC check at some point. Had they done so they would have established Nicola Edgington's history for manslaughter which may have influenced their future decisions. Had the officers established her history and passed it to the staff at the A&E department this may have ensured that she was given a higher priority."

A similar view was taken of staff who took one of Edgington's 999 calls, the report saying: "Had a PNC check been carried out, the CCC [communications control centre] staff would have been aware of Nicola Edgington's history and could have notified hospital staff so that more urgency might have been applied to the situation."

The report also concluded that while the two officers directly involved, PCs Daniel Phillips and Matthew Payne, could not have initially detained Edgington under section 136 of the Mental Health Act as the minicab office was private property, they could have done so when she followed them outside after they had taken her to the hospital.

The IPCC commissioner, Sarah Green, said it was "of great concern" that no check was made. "Without this PNC check, both the police and staff at Queen Elizabeth hospital, Woolwich, were without crucial information which may have influenced their future decisions, increased the urgency of the situation and could have escalated the medical attention she was given."

The IPCC report is not considering the actions of hospital or psychiatric staff involved in the case, something investigated separately. It does, however, note that Edgington's details from the Multi-Agency Public Protection Arrangements scheme, intended to deal with potential re-offending, were not passed by medical staff to local police, as should have been the case.

At Edgington's trial the prosecution argued she had been wrongly diagnosed with schizophrenia and had a borderline personality disorder rather than a mental illness.

The judge, Brian Barker, told Edgington her acts had been "consistent and calculated". He said: "You are manipulative and exceptionally dangerous. What you did could not have been more selfish. I disagree that the responsibility for these acts can be laid on others. You made your choice and these were terrible acts for which you must take responsibility."

Hodkin's family have asked why Edgington was freed in 2009. They said: "We cannot quite understand how or why Nicola Edgington was released back into society so soon after killing her own mother. Her release in 2009 didn't involve any independent psychiatrists or mental health tribunals; the Ministry of Justice simply followed recommendations from the Bracton Centre, where she was being held. This cannot have been the right decision."