Once my patient's testicles are secured in the electric ball crusher, I inform him that he'll be undergoing an excruciating electrical sterilization. The voltage on his crushed, flattened testicles will be turned up higher and higher until he's completely sterile, fried from the inside out. To assist his neutering, I add electric bands to his cock, zapping it as well.
He screams and thrashes but we won't be finished until he's left sterile and emasculated.