A former German nurse admitted to the court that he had been charged with killing 100 patients.

At the start of his new trial to look into other facts, former nurse Nils Hoogle admitted to the charges against him before the Court of Appeal in the city of Oldenburg, without the court being specifically exposed to the facts of the murder alone.

Hoogl admitted to a psychiatrist that he killed about thirty people. Hoogle was trying to impress his colleagues by reviving those patients, but he was unable to revive many of them and died, according to investigators.

"If Huigel is convicted of all these killings, he will become one of the worst murderers in Germany since World War II," the BBC's Berlin correspondent said.

"Yes," Hoogel responded to a question from the judge on whether the 100 charges - ranging from ill-treatment to murder - were true.

Hojl, 41, was supposed to inject patients between the ages of 34 and 96 years with drugs that led to their deaths, while working as a nurse in two hospitals, one in Oldenburg and the other in the city of Delmenhurst, Lower Saxony.

It is reported that Huigel killed 38 patients in Oldenburg and 62 patients in Delmenhurst in northern Germany between 1999 and 2005.

The prosecutor stated that the accused committed his crimes treacherously and out of spiteful motives, and the trial was transferred to a conference room because of the high attendance.

Hooghle was sentenced to life imprisonment three years ago for the murder of six patients in the intensive care unit of Delmenhurst Hospital. The court was then found guilty.

The current trial will not change anything from the previous verdict, but the ruling on him may have implications for whether he can get out of prison again.

According to the prosecution, Hoogl had injected his patients with drugs with deadly side effects, and was then trying to save them; but he failed in many cases.

Prosecutors pointed out that the motive of these crimes was his feeling of boredom and his quest for the appreciation of his colleagues, after proving to them their abilities in the recovery of patients.

The case is complex and expensive. The prosecutor requested hearing of 23 witnesses and the presence of 11 toxicology and medical law experts.