Hoegel is accused of killing the patients at a hospital in the northwestern city of Oldenburg between 1999 and 2002, and at another hospital in nearby Delmenhorst from 2003 to 2005.
He promised Hoegel a fair trial.
He was rarely successful and in 2005 was caught in the act. He said his grandmother and his father, who were both nurses, had been his role models for going into the profession.
"The prosecutor's office assumes that he did this in order to create a life-threatening situation in order to demonstrate his resuscitation skills to colleagues and superiors", the indictment states, according to DW.
"We have fought for four years for this trial and expect Hoegel to be convicted of another 100 killings", said Christian Marbach, representing the patients' relatives.
Hoegel himself said he craved "the positive feedback" he got for saving a life and used painkillers to deal with "the stress" of the job.
It was then that Hoegel confessed to his psychiatrist at least 30 more murders were committed in Delmenhorst, prompting investigators look at suspicious deaths in Oldenburg.
Officials said the total number of victims might never be known because some of bodies were cremated.
Hoegel said he had kept quiet "out of shame" and because it had taken him a long time to realise the full scope of what he had done.
"I hope he will be found guilty on each count so that the loved ones can finally find some closure", said Petra Klein, who runs the local chapter of the victims' aid group Weisser Ring.
In prior hearings, Hoegel is reportedly said to have been seeking a sense of euphoria after having resuscitated a patient from an emergency situation he himself created.
However, a police investigation concluded that he could have been stopped earlier if the two hospitals had not "failed to report the disturbing increase in fatalities when Högel was working", says Deutsche Welle.
After a minute of silence in the courtroom for the victims, the bearded, heavyset Hoegel listened impassively, his head lowered, as public prosecutor Daniela Schiereck-Bohlmann read out the name of each dead patient and the charges against the defendant.
Relatives of his alleged victims packed the court. In some cases, patients survived the ordeal, but records show that fatality rates regularly increased when Hoegel was on shift.
- Austria to withdraw from United Nations migration agreement
- China defends decision to ease rhino, tiger parts ban
- Ecostore Joins Ellen Macarthur Foundation's commitment
- Twitter Could Remove ‘Like’ Button to Promote Healthy Debates
- With the only Russian aircraft carrier has been a serious emergency
- Brazilian footballer Daniel Correa murdered, found nearly beheaded with genitals severed
- Hyundai working on solar roof charging system
- Chief Turkish prosecutor:Saudis strangled Khashoggi
- Nature pushed to the brink by 'runaway consumption'
- Facebook beats Q3 earnings expectations but user growth remains tepid