1. Pure evil au pair
It was the question on everyone's lips in the trial earlier this month– why would Yoselyn Ortega, a seemingly innocent nanny, murder her charges Lucia, six, and Leo, two, in the cold blood?
Finally, in a case that shocked the world, Ortega admitted why she viciously stabbed two innocent children. "I had to do everything, and take care of the kids. I worked as a babysitter only and she wanted me to do five hours of cleaning each week," the 55-year-old said, blaming the kids' mother Marina Krim for her crime.
On October 25, 2012, Marina panicked when she and her daughter Nessie, three, arrived at Lucia's ballet class to discover she hadn't arrived. Marina rushed back to her Manhattan, US, home to find her children in a blood-splattered bathtub and a kitchen knife dumped in the sink.
Ortega had stabbed Lucia 30 times and slashed Leo's throat. The nanny then plunged the knife into her own neck in front of Marina. Jurors gasped in horror when Ortega's lawyers argued insanity, saying the once-trusted nanny was too sick to understand the consequences of what she had done. But Judge Gregory Carro referred to Ortega as "pure evil" before she was convicted of murder and handed a life sentence, with no parole.
2. Aunt behind bars
Marquita Burch was babysitting her one-year-old nephew William Cunningham in her Cincinnati, US, home in May 2012 when she called the police saying the little boy had wandered off from the park.
While police, firefighters and neighbours searched for more than five hours, Burch's story began to unravel. Eventually the 26-year-old confessed the toddler had injured himself and she'd panicked, stuffed him into in a garbage bag and stashed him in her cousin's house.
By the time police found the tiny tot, he'd been dead for 48 hours. Before being charged with endangering a child, murder and abuse of a corpse, the judge said, "It is bad enough that Burch injured the child, but horrible to think of the child's suffering."
She was sentenced to at least 19 years in jail.
3. Teen terror with no remorse
It was Karl McCluney's 15th birthday on the day he was babysitting Demi-Leigh Mahon while her mother popped out to the shops in Manchester, UK.
Rather than try and appease the two-year-old when she started crying, McCluney flew into a rage, biting, kicking and punching the little girl, leaving her with 68 injuries and brain damage. She died two days later.
At the trial, McCluney admitted the only motive for killing Demi was that she was annoying him with her screams. The court heard that after the attack, McCluney watched TV as Demi lay unconscious on a mattress.
When her mother Ann-Marie McDonald returned home after 90 minutes and screamed, asking why he hadn't called an ambulance, McCluney claimed, "I haven't done nothing."
He then said the toddler had fallen over in the park. He showed no emotion in court and kept his head bowed while the details of his crime were revealed. The teenager admitted to manslaughter but the jury found him guilty of murder.
He was sentenced to 15 years in jail.
4. Revenge stabbing
Elzbieta Plackowska, 45, was caring for her seven-year-old son Justin and a friend's five-year-old daughter, Olivia, in a Chicago, US, condo in 2012, when the kids refused to settle down for bed. In a frustrated frenzy, she grabbed a kitchen knife, told them they were "going to heaven" and stabbed them to death.
While being interrogated, she was adamant someone had broken in and killed the children while she was out having a cigarette. However, she finally admitted she murdered her son to get revenge on her husband and she killed Olivia because she had witnessed the murder.
Plackowska pleaded insanity, but the judge sentenced her to life behind bars for murder.