10. Renée Acoby, Canada - As of 2017, Renée Acoby holds the dubious distinction of being the sole female dangerous offender in all of Canada. “Dangerous offender” is a recognized Canadian legal term. A convicted criminal categorized as such can be put in jail for an indefinite period. But just what has Acoby done to belong to this ill-starred club?

. 10. Renée Acoby, Canada - In fact, Acoby’s prison career began in 2000 when she was just 21. The young woman was handed a three-and-a-half-year sentence for drugs offenses and assault with a weapon. The crimes came after a hard childhood and teenage years. But for the most part, Acoby’s offending has actually taken place behind bars. Because by the time she’d been in jail for three years, her sentence had increased to 21 years after more than one attempt to take hostages and some violent outbreaks in prison. Bad behavior also cost her custody of the daughter she had given birth to behind bars.

9. Juana Barraza, Mexico - Juana Barraza’s first claim to fame was as a Mexican professional wrestler who went by the name of “The Lady of Silence.” But her name then became infamous after she was arrested for the murder of an 82-year-old lady who had been asphyxiated with a stethoscope. Indeed, even before she was caught, the deaths of several elderly women had led the media to dub the serial killer “La Mataviejitas,” Spanish for “old lady killer.”

. 9. Juana Barraza, Mexico - Barraza faced trial in 2008. Prosecutors claimed she had killed as many as 40 women, all aged over 60. And in the end, she was convicted of committing 11 murders and received a whopping 759-year sentence. The maximum sentence allowed in Mexico is only 60 years. But given that Barraza was 51 years old at the time, she’ll likely spend the rest of her natural life behind bars anyway. And given her crimes, few would argue with that.

8. Catherine Birnie, Australia - Australian couple Catherine and David Birnie hit the headlines in November 1986 when they were arrested for the abduction and rape of 17-year-old Kate Moir. The teenager had taken a lift from the pair before they attacked her. However, she had managed to escape and inform the police. It turned out she was the only one of the Birnie’s victims to survive. Police found four bodies buried in the backyard of their property.

8. Catherine Birnie, Australia - At their trial, the Birnies were each given four life sentences after pleading guilty to four murders. Catherine Birnie has been serving her sentence at the Bandyup Women’s Prison, where it she works as a librarian. David Birnie killed himself in Casuarina Prison in 2005. Catherine Birnie has repeatedly been denied parole and in 2009 Attorney-General Christian Porter announced that she would never be released.

7. Rebecca Butterfield, Australia - Rebecca Butterfield’s first period of jail time came in 1996 when she was convicted by an Australian court of drug offenses, unlawful entry and malicious damage. But her crimes started to spiral out of control in 2000 when she was jailed again for stabbing a neighbor who had apparently been trying to stop her from self-harming. During her three-year sentence for that crime, she attacked another prisoner, Bluce Lim Ward, inflicting 33 stab wounds.

7. Rebecca Butterfield, Australia - Butterfield received a 12-year sentence for manslaughter for the killing. However, during that sentence, she committed a string of assaults on other prisoners and staff. In 2016, at the age of 41, Butterfield was actually due for release but was sentenced to a further five years because of her very violent tendencies. Indeed, Butterfield is actually so violent that she has to be shuttled between two high-security prisons in order to give guards some respite.

6. Kathleen Folbigg, Australia - Australian criminal Kathleen Folbigg is serving a 40-year sentence for killing four of her own children over an eight-year period from 1991. Folbigg’s own father murdered her mother in 1969, stabbing her 24 times. She married Craig Folbigg in 1987 and they had four children together. Caleb died just 19 days after his birth in 1989, Patrick died at the age of eight months, Sarah at 10 months, and finally, Laura, born in 1999, died at 19 months old.

6. Kathleen Folbigg, Australia - Folbigg stood trial in 2003 at the Supreme Court of New South Wales, Australia. After the guilty verdicts, she was sentenced to 40 years in jail with no possibility of parole for 30 years. A 2005 appeal saw her sentence reduced to 30 years with no parole for 25 years. Folbigg is locked up at the maximum-security Silverwater Women’s Correctional Centre. She’s caged in the segregation unit to protect her from other prisoners.

5. Rosemary West, United Kingdom - Rosemary West and her husband Fred were two of the United Kingdom’s most notorious and depraved serial killers. She met Fred when she was just 15 and he was 28. The two started living together at a caravan park with Fred’s daughter and stepdaughter. The couple was convicted of sexual assault of a young girl in 1973. Rosemary worked as a prostitute and encouraged her husband to sexually abuse his daughter, abuse which she also participated in.

5. Rosemary West, United Kingdom - From the early 1970s, Rosemary and Fred murdered at least ten girls, including 16-year-old Heather, their own daughter. Fred was arrested for raping another daughter, with Rosemary also taken into custody for child cruelty. But the trial collapsed when the daughter declined to testify. However, the case prompted a thorough investigation and in November 1995 Rosemary was convicted of ten murders. She was eventually given a whole-life sentence, which she is serving in County Durham’s Low Newton prison. Fred, who had confessed to 30 murders, killed himself in prison before trial.

4. Katherine Knight, Australia - Katherine Knight was born in Australia in 1955 and was given a life sentence without parole for the murder of John Price, her partner. This domestic murder may seem mundane compared to the other crimes featured in this round-up of dangerous women. But once you read the details of her gruesome crime, you’ll see why she’s included – and why she was the first Australian woman ever to be given such a stern sentence

4. Katherine Knight, Australia - In October 2001, neighbors noticed that there was blood on the front door of Price’s property and alerted police. Knight was found in a coma in bed, having overdosed on pills. Price’s body, or most of it, was found in the hall. After stabbing him 37 times, Knight had skinned the body and hung the skin on a butcher’s hook. She’d then cut off his head and cooked some body parts, serving the flesh with vegetables and gravy and laying the plates out with place names – the names of Knight’s children.

3. Joanna Dennehy, United Kingdom - Joanna Dennehy was 31 in 2013 when a judge sentenced her to spend the rest of her life behind bars for the murder of three men. The case came to be known as the Peterborough Ditch Murders as all three of her victims were found in ditches near the English city. She killed the three men by stabbing in the space of just 10 days and then stabbed two more men in another town.

3. Joanna Dennehy, United Kingdom - During sentencing, Mr. Justice Spencer recounted that Dennehy had told a psychiatrist that she committed the crimes “to see if I was as cold as I thought I was. Then it got moreish and I got a taste for it.” While in prison before trial, Dennehy plotted an escape that involved the killing of a prison guard and chopping off one of his fingers to use on the prison’s fingerprint security system. Fortunately, the plot was revealed before she could put it into action.

2. Roshonara Choudhry, United Kingdom - While all of the women described here are scary, Roshonara Choudhry is the only one who was a terrorist. Born in East London in 1989, Choudry had been in the final year of a degree course at King’s College London. But she stopped her studies not long before she made an attempt on the life of a British Member of Parliament in May 2010, driven by her support for al-Qaeda.

2. Roshonara Choudhry, United Kingdom - At her trial, the jury was told that she had attended an open session organized by MP Stephen Timms at a local library. Pretending to shake his hand, she’d stabbed the MP twice in the abdomen. Timms survived the attack and still sits in the House of Commons. Choudry was found guilty of attempted murder and jailed for 15 years, which she is serving in the maximum-security Bronzefield Prison.

1. Marybeth Tinning, New York - Born in Duanesburg, New York in 1942, Marybeth Tinning had a series of low-status jobs before Ellis Hospital in Schenectady took her on as a nurse’s aide. She married Joe Tinning in 1965. Their first child came in 1967, to then be followed by seven more. The couple also adopted a child, making a total of nine children. By the end of 1985, every one of the children was dead.

1. Marybeth Tinning, New York - Some of the deaths had been put down to sudden-infant-death syndrome, while others had been put down to to various illnesses. But during a police investigation of the last child’s death, Marybeth confessed to killing three of the youngsters. Ultimately, she was only charged with one murder. Found guilty at her 1987 trial, she was sentenced to 20 years to life and, repeatedly denied parole, is serving her time at Bedford Hills Correctional Facility for Women.