From killing for money to twisted abuse and psychopathy, each of these serial killer couples will make you sick to your stomach.

As well as being illegal and morally repugnant, committing murder is risky. The chance of getting caught is high enough when only one person does it; adding a second perpetrator only heightens the potential for error, and thus the likelihood of imprisonment.

Since spouses in the United States and Canada can’t be forced to testify against one another, enlisting your betrothed might seem like a smart move, but as these infamous and horrifying serial killer couples show, things can and still do end badly…

Serial Killer Couples: Paul Bernardo and Karla Homolka

A gruesome pair even among serial killer couples, Paul Bernardo met Karla Homolka in mid-1980s Toronto, at which point Paul had already committed multiple rapes, Karla was 17 at the time; Paul was 23. The story goes that the two were drawn to each other almost immediately, but there apparently was a problem: Karla wasn’t a virgin.

To “solve” it, Karla said in subsequent testimony that she wanted to give her sister Tammy’s virginity to Paul that Christmas. One night, Karla decided to drug and bind her virginal 15-year-old sister so Paul could rape her.

Somehow, the end result was even worse than what the pair had planned. After filming themselves raping and abusing Tammy’s inert body for hours, the couple retired to bed, leaving Karla’s sister tied up and unable to move. Sometime during the night, Tammy choked to death on her own vomit and died. The inquest found no evidence of foul play, despite the binding marks and violent rape, which were apparently overlooked during the autopsy.

Paul and Karla repeated the grotesque act twice more, killing 14-year-old Leslie Mahaffy and 15-year-old Kristen French. Paul also continued to rape other women in the meantime, which is how his DNA wound up in authorities’ hands.

He also made the mistake of beating Karla in 1993, after which she struck a deal with the authorities and started giving testimony, leading police to the videotapes of the murders.

Paul is currently serving life in prison, while Karla (who claimed she was abused and forced to help Paul in his murderous schemes) put in 12 years from 1995 to 2007. She’s free now, and the mother of three kids, while Paul is eligible for parole in 2018.

Ian Brady And Myra Hindley

Ian Brady and Myra Hindley killed five children in England between 1963 and 1965, in what became known as the Moors Murders, a string of crime that stands out even among those of other serial killer couples. Brady was born in 1938 and raised by a chaotic sequence of foster homes and juvenile detention centers throughout his early years.

By 1961, when he met Hindley, he already had dozens of convictions for burglary and assault.

This serial killer couple fell in love and stayed up late into the night reading stories about Nazi atrocities to each other. They also rented a van and robbed a few banks. Sometimes, Ian would drug Myra and rape her, which she confessed to her sister made her feel more in love than ever before.

The couple killed their first victim, 16-year-old Pauline Reade, in July 1963. After raping and beating her, the couple dug a shallow grave on the moors outside Manchester and buried her body. On November 23, 1963, they killed their second victim, John Kilbride, in much the same way. In December 1964, Myra enticed 10-year-old Lesley Ann Downey into her van and brought her home to Ian for what, by now, was their usual routine. This time, Myra made an audio recording of the murder.

As often happens among homicidal lunatics, Ian and Myra eventually took things too far. In October 1965, Ian brought home 17-year-old Edward Evans, a boy he had picked up at the train station. Once home, Brady beat him to death with a shovel in front of his 17-year-old brother-in-law, David Smith. Smith helped dispose of the body, but then he went home and told his wife. And then he told the police.

Both killers expressed remorse after getting their life sentences. Myra claimed it was all Ian’s fault, but told the court she regarded herself as worse than her partner since she had done most of the enticing. Ian took responsibility for what he had done, never asked for parole, and refuses to seek release from the secure mental hospital he’s been confined to since 1985. Myra died of pneumonia in 2002, aged 60.

Serial Killer Couples: Gerald And Charlene Gallego

In just a two-year period, from 1978 to 1980, Sacramento-area couple Gerald and Charlene Gallego, who rank among recent memory’s deadliest serial killer couples, murdered at least ten young people, often two at a time. Their usual method was to cruise area malls looking for teenage girls, whom Charlene would lure into their van with promises of free marijuana.

Once the girls got into the van, they were confronted with an armed Gerald, who forced them into the cargo area and bound them up for a ride out to the countryside. The victims were invariably raped, beaten, and murdered, with their bodies dumped in scattered locations from the Sierras to the Nevada desert.

The last killings were of 22-year-old Craig Miller and his fiancée, 21-year-old Mary Elizabeth Sowers, who were kidnapped at gunpoint from the Arden Fair Mall. Gerald forced the young couple into his van in plain sight of the victims’ friends, who managed to catch his license plate number and alert the police.

Gerald shot Craig right away, then he and Charlene took Mary to their apartment, where they raped and tortured her for several hours. Eventually, they drove her out of town and shot her three times.

It wasn’t long before Gerald and Charlene’s relationship hit the rocks. Shortly after their arrests, Charlene struck a deal to testify against Gerald – who she said was 100 percent to blame for everything – in exchange for a change of venue. In 1984, Gerald was given the death penalty, but the sentence was later commuted to life. He died of colorectal cancer in 2002.

Charlene served 16 years, always insisting she was practically an innocent bystander who couldn’t have done anything to stop Gerald. Today, she’s back out and living under an assumed name in Sacramento.

According to a 2013 CBS interview, Charlene is active in veterans’ charities and maintains she had no choice but to commit such atrocities as burying a pregnant woman alive and leaving bite marks all over several victims, one as young as 13.