Delving into the stories of killers who broke the Hippocratic Oath to use their medical knowledge for murder, taking the lives of often vulnerable victims instead of caring for them.
John Brown: When a man is found dead in a San Diego motel, minus his leg, police initially believe it's the result of a car accident. (S4, ep 1)
Jack Kevorkian: Dr Jack Kevorkian assisted the death of a terminally ill patient live on TV. Kevorkian is tried for murder and the nation is split. (S4, ep 2)
When Samira Frasch is found dead at the bottom of the pool, police begin to investigate her husband. Did he stage the scene to hide his crime? (S4, ep 3)
The suicide of a beauty queen leaves her loved ones in shock. However, evidence suggests she didn't die by her own hand. Detectives try to find who is guilty. (S4, ep 4)
Mother, Karen Sharpe dies in a shooting but who would want to kill her? Investigators soon uncover Karen is in the midst of a multi-million dollar divorce. (S4, ep 5)
Administrators notice death rates in their intensive care unit have risen sharply. Suspicions fall on a nurse who turns out to be Germany's most prolific murderer. (S4, ep 6)
When a resident dies at a care home it's assumed she passed away peacefully but an autopsy reveals horrific injuries. Can a quiet, young carer be responsible? (S4, ep 7)
A care home resident is discovered dead, starting a murder investigation. When the suspect then becomes a victim of violent attacks, is someone else responsible? (S4, ep 8)
A Texas serial killer preys on elderly victims. His murderous death toll is suspected of having amounted to 22 before a sinister clue leads to his capture. (S4, ep 9)
Another killer who broke the Hippocratic Oath to use their medical knowledge for murder, taking the lives of often vulnerable victims instead of caring for them. (S4, ep 10)