Katie approached the autopsy table and stared down at Billy Hagerty’s naked body in disbelief. His head was still misshapen from the two bullets that had burst inside it, although Dr Kelley had done her best to reassemble his face, so that at least he was recognizable. There was another entry wound about three centimetres below his ribcage, on the right-hand side.

It wasn’t the bullet wounds, though, that riveted Katie’s attention. It was the two diagonal scars, one on either side of his chest, and the deep puckered scar over his left hip. Most of all it was his genitals: his penis was erect, but bent downwards and sideways against his thigh, and his scrotum was nothing more than an empty bag of smooth skin, not wrinkled as she would have expected a scrotum to be.

She looked across at Dr Kelley and Dr Kelley nodded.

‘Yes. Billy Hagerty’s a man, but he’s a transgender man. He used to be a woman. He’s had a bilateral mastectomy and his chest has been reshaped to give it more masculine contours. That’s what we usually call “top surgery”. From the scars on the lower pectoralis muscle, I would guess that he used to have quite large breasts.’

Katie said, ‘I’ve heard of this, of course, but never seen it in the flesh. It’s amazing.’

‘You can see by the scar here across the lower stomach that he’s had a hysterectomy – his uterus taken out. He’s probably had a BSO, too, a bilateral salpingo-oophorectomy, which means that both ovaries and fallopian tubes have been removed. This we call “bottom surgery”.’

‘And his genitals? How was that done?’

‘His penis was formed out of this tissue graft from his hip. There’s a prosthetic inside it with an outer coating of silicone and interlocking plastic joints. All he had to do to get an erection was bend it upwards by hand. He’s had the simplest and the cheapest prosthetic. You can get more expensive ones, which are pumped up with reservoirs of saline water inside the scrotum, although those don’t tend to last so long and quite often they can go wrong and have to be taken out again.’

‘It’s so hard to believe that he was once a woman. I mean, he’s so masculine-looking. He has stubble on his chin.’

‘Well, that’s the testosterone. His urethra was rerouted through his new penis so that he could urinate standing up like any other man. You can see that his outer vaginal lips, his labia majora, they’ve been joined together to form his scrotum. Usually he would have been given prosthetic testicles, but this obviously hasn’t been done yet. Maybe he wasn’t ready for them.’