Mary Ann Cotton, long regarded as one of the North-East's most notorious killers, has become the subject of modern police attention.

FEW killers have intrigued more amateur sleuths and experts than Mary Ann Cotton, whose very name has become synonymous with arsenic poisoning. Hanged in Durham Prison in 1873 for the murder of her stepson Charlie, she protested her innocence to the end. But she was reviled by those who saw the finger of guilt pointing at her for the deaths of many people close to her. Others took a kinder view and considered her just unlucky and touched by some unknown curse.

That the grisly case still has the power to fascinate is evidenced by exhaustive research carried out by former Northumbria Police Detective Superintendent Stephanie Yearnshire and her husband John - also a retired police officer and forensic expert of 21 years standing.

Applying modern policing skills and knowledge, they have picked over the bones of old evidence to flesh out a new insight into the life and times of Mary Ann Cotton.

At Sunderland University this week, Mrs Yearnshire gave a lecture based on her research: "Wilful mass murderess or misunderstood matriarch?" She comes down firmly on the side of the former.

Her verdict is to the point: "She was calculating and quite vicious. There was plenty of evidence that she had become an adultress, bigamist, forger, fraudster, con woman, thief, inveterate liar, child abuser, lazy and vain."

She adds: "There were 21 people close to Mary Anne who died. I would not subscribe to her wilfully causing all the deaths, some were clearly due to illness and diseases of the time. But, at some stage, based on more than the balance of probability, she took over the hand of fate in a number of people's lives."

Consider the facts. Born in 1832, Mary Ann Robson was brought up in a Christian way of life. But signs of her modus operandi surfaced early. Aged 20, she left her home in Murton in disgrace, having married William Mowbray secretly, and moved to Devon, where they had five children - four of them died.

The couple moved back to the North-East living around Tyneside, before settling in West Auckland. During their wanderings, she had three more children. They died and so did William.

Mary Ann remarried to George Ward, a Sunderland engineer. He died in October 1866, barely 14 months after the wedding. A month later, Mary Ann answered an advertisement for a housekeeper for comfortably-off James Robinson, of Pallion, Sunderland. A week after her arrival his ten-month-old son died of convulsions - certified as gastric fever.

Mary Ann visited her mother in Seaham in March 1867, remarking to unbelieving neighbours that she thought her mother might die. Nine days later, her mother was indeed dead.

In the spring of 1867 there were three deaths in the Robinson household. In each case there was reported foaming at the mouth and retching after being given a drink. Again, death certificates recorded the cause of death as gastric fever.

Mrs Yearnshire says: "It is thought the children were in the way of her having a comfortable life as she did not want to look after them and they were insured."

Mary Ann married Robinson when she was five months pregnant. Their baby lasted a few months and died of gastric fever. Robinson discovered at one stage his wife was pawning his clothes. It is not known what she spent the money on, but she did have an unusual habit for a working class woman - of paying others to do her housework or shopping.

Mary Ann left Sunderland after six years, during which time ten people close to her died. She then became the lover of Frederick Cotton. His sister Margaret died of severe stomach pains while Mary Ann was at the house.

In September 1870, heavily pregnant, Mary Ann bigamously married Cotton. Four weeks later she filled in insurance proposals on the two Cotton boys and moved to West Auckland. A year later, well insured, Frederick Cotton took ill and died. And her lover, Joseph Nattrass, moved in as lodger.

She advertised her services as a nurse and started looking after West Auckland Excise Officer Quick Manning, who allowed her to bring her lover Nattrass, with her.

Then, in March 1872, Frederick's ten-year-old son by an earlier marriage died. And 17 days later, Mary Ann and Frederick's ten-month-old son passed away. Nattrass succumbed a month later.

Her remaining stepson, Charlie, remained an obstacle and, in July 1872, when she found she could not place him in a workhouse by himself, she remarked: "Perhaps it won't matter, as I won't be troubled long. He'll go like the rest of the Cotton family." A week later he died.

An initial inquest verdict of death by natural causes was overturned when arsenic was found in Charlie's stomach contents, setting in train one of the most celebrated murder trials the region had seen.

In one of the earliest cases of "airbrushing", newspapers had deliberately coarsened Mary Ann's features in pictures, in contrast to the "appealing looks, delicate and prepossessing appearance" noted by reporters.

Mary Ann's line of defence was that the green wallpaper in Charlie's room was heavily impregnated with arsenic. But the court had heard that Mary Ann had once been a nurse in Sunderland, where she learned all about drugs and poisons and the jury, filled with stories of her bigamy which newspapers had exposed, found her guilty of murder on March 8, 1873.

Mrs Yearnshire says: "Many of her victims died of gastric fever, which was a Victorian euphemism for intestinal disorders from typhoid to diarrhoea - diarrhoea was also a symptom of arsenic poisoning.

"Widely available, arsenic was used in soft soap used to clean bugs from beds, or as part of sticky flypaper."

She adds: "Nationally there was concern about the prevalence of child mortality by poisoning, especially where there were insurance or charity club payments. Behavioural criminologists today may argue that, like Crippen, Mary Ann saw those around her as commodities, rather than human beings.

"There are clear patterns and modes of behaviour. She sought housekeeping or nursing roles with recently-bereaved or sick men to gain entry to their lives. She was willing to engage in early sex and early pregnancy to tie the men she married and she married secretly, always giving false details.

"She also moved around from place to place and this, more than anything else, impeded detection. And, most ominously she warned others of deaths where they were unexpected."

Summing up Mary Ann's character, Mrs Yearnshire says: "All through this she came across as a person who wanted to live a comfortable life. She got other people to do her housecleaning and shopping, which she was more than capable of doing herself.

"She was calculating and quite vicious in how she dispatched people, but I don't think she saw them as human beings. In the case of the children, it was a form of post birth control, especially once she had got them insured."

Question marks may still hang over the case, although the Yearnshires may have come closer than many to pinning down the truth. But mysteries will still linger, ensuring the case is kept alive in the public's imagination.