‘Yes, though they note that rookies tend to over-examine rather than make accidental omissions. By the time the body reached his table, the syringe had been either accidentally or deliberately removed from the vein in the arm where it was found though it was bagged and labelled quite correctly, and the police photographs showed everything in close-up. Shenfield took those as being accurate and did not do any tests, for example by replacing the syringe into the vein – he signed off on the photos. That’s not a criminal omission but it’s the sort of thing a meticulous path like Shenfield would never have done. He also estimated the levels of heroin left in the system by the usual calculations, but apparently there is a recent and more accurate way of measuring those which takes different factors into account – not just time since injection, time since death, any visible effects on the liver and other tissues. Shenfield knew about the latest one because he had been asked to advise and comment – in effect he had done a peer review. This method is slowly taking over from the old one, though there is no suggestion that anyone abandon that completely – the calculations have proved reliable for forty-odd years, but in some circumstances they can be verified and backed up by the second method, and apparently the PM on Liam Payne was just such a case. They were somewhat surprised that, so far as they can tell from the report, Shenfield used only the old method of calculation.’

‘Couldn’t he have used the recent one as well and simply not noted it?’

‘Possible but very unlikely, and remember, he was known to be a stickler for detail. His path students were terrified of making so much as a slip-up in grammar let alone a scientific error.’

‘What’s the conclusion?’

‘That there is room for doubt. About the way the syringe presented in Payne’s arm, and about the amount of heroin in the system, in terms of whether it was certain to be fatal, likely to be fatal or unlikely ditto. The margin for error is there but in this sort of case – well, if we were looking at another party being involved, perhaps even administering the heroin, and if we had that person in our custody and were looking to charge him or her . . .’

‘Their brief would have a field day.’

Kieron nodded.

‘What do Adam and Dr Murray recommend?’

‘They don’t – they weren’t asked to, it wasn’t in their remit.’

‘Over to us then.’

‘It’s not a difficult decision, Simon. We have a duty towards the deceased, to his family and to the public, in that we may – or of course may not – be investigating a crime.’

‘So, you’ll apply to the coroner for permission to exhume the body?’

‘Yes, and thank God it was a burial.’

‘Depends which way you look at it,’ Serrailler said.