A Clayton County jury has received a tutorial in circumcision from an expert in the field.

Dr. Fred Kogen is a general practitioner and mohel (rhymes with “boil”)—a person trained to perform the Jewish ritual of circumcision. The jury is hearing a lawsuit from a mother who says nurse midwife Melissa Jones cut off the tip of her two-week-old son’s penis during his circumcision at Life Cycle OB/GYN in Riverdale in 2013, and that the staff, their doctors, and the clinic owner did not inform her what had happened so that she could take the steps to have the severed piece reattached.

Using attorney Jay Hirsch’s arm tucked inside the dangling sleeve of a hoodie as a teaching prop, Dr. Kogen showed the jury how proper circumcisions are done. He says the number-one lesson emphasized in training is, “You have to protect the head of the penis.”

He detailed the steps to make sure the foreskin to be cut is separated and laid flat and high as far as possible from the glans, drawing chuckles from the courtroom with an inadvertent double entendre.

“If I’m pulling on my penis, it’s going to stretch,” explained Kogen.

Kogen says there is nothing else on the body like glans tissue and once it's cut, it is catastrophic -- so everything possible should be done to save it and get it reattached. Doctors say there is a narrow window of no more than 12 hours in which that tissue is viable.

“Once there’s damage to it, and you lose a part of it, there’s no going back,” he said. “I mean, it’s really literally Humpty Dumpty. You cannot get him back together again.”

The lawsuit says the clinic put the severed piece in saline in biohazard bag, and kept it in a refrigerator for months—disposing of it when they got word that the mother had hired a lawyer.

“If I had a piece of glans that was taken off, there’s no doubt in my mind I would do the best I can to save that, and I would get in touch with someone who could use it to potentially help this baby,” said Kogen.

He acknowledges that it is a very small target.

“I’ve performed six, 7,000 circumcisions and this has never happened to me. I’ve never had a complication like this,” said Kogen, standing in front of the jury box. “This is something that —it’s not even a complication. It’s an injury that should never, ever occur if the technique is done properly.”

**An earlier version of this story incorrectly identified Dr. Kogen as a pediatrician, not a general practitioner. **