An 81-year-old German man whose defense to charges of multiple rape was that he could not get an erection won a victory on Tuesday when the country's highest court ruled he could not be forced to have his potency tested.

The Federal Constitutional Court argued that the man's human rights had been violated by lower court rulings that he be ordered to undergo hospital ultrasound and nocturnal checks on his penis.

The man, who was not named, had told the court during his trial that diabetes made it impossible for him to get an erection. One court had ruled medical staff could tie him to a bed, attach a ring to his penis overnight, and use an "erectometer" to check whether there was any stiffening.

A medical expert had said that even if the tests had been carried out, they would not have given conclusive evidence. The trial continues.