A man accused of poisoning his co-workers over the years by serving them doctored sandwiches is revealed to have acted like a scientist.

He was checking to see how his subjects reacted to various substances, a psychologist told a German court on Tuesday.

The accused identified as Klaus O, 57 was arrested in 2018 in the aftermath of 21 deaths of company employees in the town of Schloss Holte-Stukenbrock.

“Listening to his statements about his motive, he came across like a researcher who was trying to see how different substances affected rabbits.’’

While the high number of deaths initially prompted the investigation at the company, it has not been proven that any of the dead individuals were poisoned.

But he is facing attempted murder charges in the current case.

Two of his colleagues suffered serious kidney damage, while another had brain damage and is presently in a vegetative state and has to be cared for by his parents.

The psychologist had been called in to determine whether the defendant was a suicide risk.