As well as stripping him of his nursing license, the court also ruled out the possibility of parole after serving 15 years, due to the particular severity of the crime.
Having been entrusted with his patients' lives for years, the German nurse injected patients at Delmenhorst Hospital in northern Germany with enough heart medication to create medical emergencies which required resuscitations, so he could practise what he had watched doctors doing.
Some doctors had noticed that he always seemed to be around when patients were being resuscitated, often assisting junior doctors with the procedure.
But often, the nurse's injections went wrong and medical staff were unable to save the patient. The death rate at Delmenhorst hospital's intensive care unit almost doubled while Niels H. worked in the department.
During his trial, he also admitted to a psychologist to killing a total of 30 patients with overdoses of the cardiac drug and almost killing another 60 during his time at Delmenhorst.
"It was the clinical daily routine which failed to challenge me," Niels H. previously told the court, explaining that he would feel good for days after resuscitating a patient.
The number of patients nurse Niels killed is still not certain and some have dubbed the case "Germany's largest hospital serial murder."
During Niels H.'s total time in employment there were 411 deaths, 321 of them during his shift or immediately after. Of these 321, 191 people were buried - the rest were cremated.