I realised what he was going to do a split second before he did it, but she was blissfully unaware.

Still looking at me, still grinning that inane, hateful smile, my father drove his fist into my mother’s pregnant belly.

With a scream, she collapsed to the kitchen floor. I tried to get to her, but my father easily held me back. He kicked her in the belly again and again, until I finally wrested myself free of him and threw myself over my mother. She was barely conscious. A large red bloom was already spreading across the back of her skirt.

‘Stop!’ I screamed. ‘You’re killing her!’

‘Good riddance,’ my father said, drawing back his foot and aiming a kick at Mum’s head.

I leaped to my feet, and launched myself at him.

It was what he’d been waiting for. He caught me as if I was a child running into his outstretched arms in the playground.

The next second he had me in a vicious headlock, my back to his chest. I clawed frantically at his arm as he crushed my windpipe, digging my fingernails into his skin hard enough to draw blood but unable to break his hold. Everything was already starting to turn black. His breath was hot against the back of my neck. I knew he wasn’t going to stop until he killed me. And then he’d kill my mother – if she wasn’t dead already.

Somehow I summoned my remaining strength and in one last, desperate move, I lurched forward, momentarily throwing him off balance as he fell with me. His hold finally loosened and I broke free and staggered to the other side of the kitchen, coughing and gasping for air.

My father didn’t follow me. He was holding his head, bellowing with pain. Blood dripped through his fingers from a sickening gash on his forehead. There was more blood on the marble counter: he must have smashed his head on the edge of the stone with the full force of his bodyweight behind him.

He looked at me, his expression confused, as if he couldn’t work out why I was here. And then slowly he sank to his knees.

The blow to his head almost certainly wasn’t fatal. I had to call an ambulance for my mother: the paramedics would probably save him, too. And then she’d go back to him, like she always did.

No one would blame me for his injuries. Everything I’d done until now had been in self-defence.

When I picked up the cushion from my mother’s kitchen chair and calmly held it over his face until he stopped breathing, that was murder.

SETtalks | psychologies series

Science ♦ Entertainment ♦ Technology

Inside the mind of a psychopath | Original Air Date 9 July

The transcript below has been lightly edited for length and clarity.