An anaesthetist suspected of poisoning seven patients - two of whom died - appeared in court in France on Wednesday, reports the BBC.
The 45-year-old was placed under formal investigation on 6 March, but magistrates are deciding whether to remand him in custody.
Several alleged victims attended the morning hearing.
The suspect denies the charges, with his lawyer saying there are "real weaknesses" in the case against him.
He is accused of carrying out the premeditated poisonings over a nine-year period from 2008 at two clinics - the Franche-Comté and Saint-Vicente - in Besançon, a city in eastern France.
The suspect is said to have been well-regarded in his field.
According to the investigation, "lethal doses of potassium and anaesthetic" were administered to seven patients, aged from 37 to 53.
They all suffered cardiac arrest, said French news provider Europe1, quoting a judge.
A 53-year-old man died in 2008 during a kidney operation, and a 51-year-old woman died in 2016 during an operation on a fracture.