‘Quite.’ Pritchard’s expression darkened as he turned back to the monitor, using a few swipes to zoom in further still. ‘Look at the way these sinews have blackened and frayed. That’s post-shock arrhythmia, and it’s present on the other victims as well. It was almost certainly caused by sustained arrest of ventricular activity, otherwise known as cardioplegia.’

‘Hold on. Are you suggesting they all died of heart attacks?’

‘Effectively, yes.’

‘That’s ridiculous. They were all in their twenties.’

‘I appreciate that, Detective, but a heart attack can be artificially induced.’ Pritchard waved at the screen again. ‘This cellular damage is consistent with several short bursts of electrical energy between 0.5 and 0.6 amps, applied directly to the chest.’

She frowned. ‘You’re talking about defibrillation.’

‘Correct. Had the bodies been discovered within days, minor burn marks from the electrodes might have been present at the contact points, except natural decay robbed us of that evidence.’ He crossed his arms. ‘Somebody with a portable electrical device, designed to restore normal rhythmic function, intentionally used it to stop the hearts of these three young men.’

‘I didn’t know that was possible.’

‘Oh yes.’ The pathologist scratched his nose. ‘Death by defibrillator is known as the R-on-T phenomenon. I won’t blind you with science, but applying the correct voltage at a specific point in the heart’s cycle induces something called V-fib, put simply a fatal rhythm. It can also be created by sudden impacts, like a cricketer hit in the chest by a fast delivery. If such a shock comes during what’s known as the T wave, it can easily kill.’

‘So maybe that explains how.’ Hawkins looked back at the post-mortem room, where the first body was now being wheeled towards the door. ‘But why would anyone do that?’

Pritchard shrugged. ‘I think you’ll find that’s your department, Chief Inspector.’

‘Fair enough. How much training would the technique require?’

‘That depends.’ He thought for a moment. ‘Most modern defibrillators are automatic, and won’t deliver a shock unless they detect an abnormal rhythm, which we have to assume these men weren’t exhibiting. This means the killer must have used a manual unit, which delivers a shock regardless. The technology tends to be used by medically trained professionals in situations where the patient’s health is of concern. Your killer had no such interest, of course, so even if he had no experience of the technique, he could simply keep trying until he got the desired result. It would have been quite excruciating for the victims but it wouldn’t take long to stumble upon the right method. Correspondingly, your killer may have little or no prior experience with his MO.’

‘What about the equipment itself, is it hard to obtain?’

Another shake of the head. ‘You could buy one this afternoon for less than a thousand pounds.’