BERLIN (AFP) - A court-appointed expert said Thursday that a German former male nurse had admitted killing around 30 patients at a hospital where he worked, national DPA news agency reported.

The ex-nurse went on trial in Oldenburg in northern Germany in September, accused of the murder of three patients and attempted murder of two others. Investigators suspect his motive was a desire to demonstrate his resuscitation skills.

The 38-year-old defendant confessed to up to 30 killings during an examination by a psychiatric assessor, who gave evidence in the trial Thursday, DPA said.

The gravely ill patients are believed to have been injected with overdoses of heart medication between 2003 and 2005, it added. In a further 60 cases, the patients survived.

The district court in Oldenburg had already sentenced the ex-nurse to seven and a half years in jail in 2008 for attempted murder.