‘As far as hard evidence goes, the vast majority of the post-mortem examination provided no unexpected information. The victim was in good health, showed no signs of injuries received prior to Saturday night, had not had recent sexual intercourse, was not pregnant and had never borne a child.’ Cooper takes a pause and clears his throat: with that out of the way, we’re getting to the good stuff. ‘As I suggested at the scene, she suffered two sets of injuries: one to the face, and one to the back of the skull. The pattern of the facial injuries is consistent with a punch. The salient fact about this punch is the degree of damage it inflicted: the victim’s jawbone was fractured, and two of her lower left incisors were broken almost out of their sockets. Considerable force was required. I think we can safely say that the blow was inflicted by a man of above average strength and fitness.’

I mouth Strong guy at Steve. He raises his eyebrows at me: That sound like Rory to you?

‘Those injuries, however,’ Cooper says, ‘would not have been life-threatening. The fatal injury was to the right rear of the skull. This injury is linear, approximately two and a half inches long, and made by an object with a sharp right-angled edge, consistent with the fireplace surround on which the victim was found. The blow caused a severe skull fracture leading to an extradural haematoma. In the absence of immediate medical attention, the increasing pressure on the brain resulted in death.’

‘The victim took the punch, went over backwards and hit her head on the fireplace surround,’ I say. ‘How long would it have taken her to die?’

‘Impossible to say. An extradural haematoma can cause death within minutes, or within hours. Given the severity of the injury, I would have expected this one to progress fairly rapidly; precisely how rapidly, however, there is no way to know. One possible indicator, however, may lie in the second injury to the right rear of the skull.’

‘Whoa,’ I say. ‘Second injury?’ Steve’s eyebrows go up. I kick my chair closer to him, switch on speakerphone and put a finger to my lips. Cooper hasn’t made up his mind about Steve yet; one wrong word out of him could end the conversation right there. I feel a weird, idiotic twitch of triumph, like the bad kid seeing her golden little brother in the doghouse while she gets the pats on the head for once. I slap it down.

‘Restrain your excitement, Detective,’ Cooper says. ‘This second injury is minor – a slight contusion. Apart from that, it is practically identical to the first: linear, two inches long, made by an object with a right-angled edge. The two injuries are parallel, lying approximately a quarter of an inch apart, which explains why the second was not immediately obvious at the scene.’ He sounds miffed at the thing for hiding out on him.