According to the Evidence (32 page)

‘In plain language, can you explain what led you to this conclusion?' asked Lewis Gordon.

‘The samples I took included blood, urine and the fluid extracted from the eyeballs, called “vitreous humour”,' explained Smythe. ‘I ran analyses for barbiturates, as there was a vial of sodium Pentothal recovered from the premises, but none was discovered. There was a substantial amount of morphine in the blood, consistent with the painkilling use of that drug, but it was not in a lethal range. As to potassium, it was useless to seek it in the blood, as that substance leaches from the cells after death and a high value would be meaningless, even if extraneous potassium had been injected.'

‘So how did you arrive at your conclusion that an excess of potassium had been administered?' asked Gordon, though he knew the answer full well.

‘I said that the blood is useless because of rapid contamination from potassium in the body cells – but there is a place in the body which is insulated from this effect, where potassium remains at the same level as during life. This closed-off place is the fluid within the eyeball – and I found very high concentrations of that substance in the samples I took from both eyes.'

Again sibilant murmurs ran around the court, causing the judge's head to jerk up in disapproval.

‘You are sure about this, doctor? Absolutely sure?' asked the prosecuting counsel, wishing to fix the vital point in the minds of the jury.

‘I am in no doubt at all, sir,' grunted Angus. He shuffled some papers on the edge in front of him and stabbed a big finger at one page.

‘The normal potassium level during life is about twenty milligrams in each hundred cubic centimetres, but my analyses revealed an average of no less than fifty-eight!'

He looked up and glared at the jury defiantly. ‘The tests were run in duplicate on the fluid from both eyes and all four results were within the expected limits of analytical error.'

He tapped his papers together into a neat sheaf and waved them at the court. ‘There can be no doubt at all that high potassium level – three times the normal amount – could only have been attained by a considerable amount of the substance being injected into the bloodstream, thus finding its way into the eye fluid.'

Just to seal the fact in the minds of the jury, Lewis Gordon added a supplementary question. ‘You say that the only way potassium could get into the eyeballs would be from an injection. Do you exclude any other means, such as taking potassium by mouth?'

‘Absolutely!' snapped the pathologist. ‘Potassium is present in all kinds of food, especially fruit. It is even given as a medicine for bladder and kidney infections, but it is selectively absorbed and excreted, and its concentration in the blood is regulated within a very tight range, so that it could never reach these very high levels that I found in the eye fluid.'

‘How does potassium chloride cause death, Dr Smythe?'

‘It poisons muscles, causing irregularity of contraction. The most immediate effect is on the heart muscle, disturbing the rhythm of its beat.'

The prosecuting barrister pursued these matters in more detail, to emphasize the serious and indeed lethal effects of the substance. He led Angus Smythe to confirm that death from an injection of a large amount of strong potassium chloride solution would kill within minutes.

‘That is why vets use it to put down animals,' he said gruffly. ‘They usually precede it with an injection of Pentothal or some other barbiturate, to literally put the animal to sleep, as the effects of potassium, though very rapid, can be distressing as the heart fails.'

Final questions elicited the fact that Dr Smythe discounted the presence of the advanced cancer as the cause of death. ‘There were no catastrophic complications, like an internal haemorrhage or a pulmonary embolism – that's a clot passing to the lungs. And given the potassium findings, there is no need to invoke the general effects of cancer, advanced though that was.'

Lewis Gordon spent a few more minutes questioning the dogmatic Scotsman, though what he was really doing was covertly going over the same ground, intent on impressing on the jury that this was the crux of the evidence, that Mrs Mary Parker was virtually awash with potassium, which could only have been the sole cause of death. He pressed this point as far as he dared, until he sensed that the judge was beginning to get restive with his attempts at repetition.

‘That is the prosecution case, my lord. I am calling no other witnesses,' he said, with an air of finality that suggested that nothing else was required for a guilty verdict.

Mr Justice Templeman peered down over his glasses at the defence counsel.

‘You wish to cross-examine, Mr Prideaux?'

Nathan rose to his feet and smiled almost ingratiatingly at the judge.

‘I do indeed, my lord, but I would like to crave your indulgence concerning the order in which we proceed.'

Templeman looked suspiciously at the Queen's Counsel, who continued. ‘As your lordship must be very well aware, the whole thrust of the prosecution case lies with the evidence of this witness. It would greatly facilitate my cross-examination – and indeed the course of justice – if I could call my only witness first, so that the evidence of Dr Smythe could be put into context with that of my expert.'

There followed some minutes of complicated legal argument, before which the jury were led out and Angus Smythe, looking irritated at the delay, stood down from the witness box to sit at a nearby empty chair. The judge and the two leading counsel engaged in an almost private debate, phrases such as ‘natural justice', ‘facilitating proper understanding' and ‘outwith normal criminal procedure' were bandied about.

‘What's going on?' Moira whispered to Doris. ‘Why have the jury been chucked out?'

‘This is all a bit irregular, as the prosecution normally have to finish completely before the defence have their turn,' murmured the lawyer's secretary. ‘The jury mustn't be influenced by any goings-on that might affect their verdict.'

However, they soon returned, shuffling back to their places, as it seemed that with the judge's acquiescence the prosecution barrister had shrugged his agreement to Nathan's request.

Templeman turned to the jury to soothe them.

‘That was nothing to do with the facts of the case, gentlemen, it was a legal discussion about a procedural matter.' He nodded at Prideaux and, pleased with his manoeuvre, the defence counsel called Richard Pryor to the box. Moira watched with mixed excitement, pride and foreboding as her hero mounted the steps, took the oath and identified himself in response to Nathan's questions.

‘Dr Pryor, for how long have you been a pathologist?'

‘About sixteen years. I began before the war, then I was a Senior Specialist in Pathology in the army until 1946.'

‘And since then, you have been a full-time forensic pathologist?'

‘Yes, I was Professor of Forensic Medicine in the University of Singapore until last year, when I entered private practice in that speciality, recently being appointed to the Home Office list.'

Richard said all this in a matter-of-fact way, free from any hint of aggrandizement. Nathan leaned forward against his table, as if reaching out to the witness.

‘You were engaged by the defendant's solicitor to review the medical evidence in this case, doctor. You have heard what Dr Smythe said, what do you say in response?'

Richard faced the jury, paused and then began speaking with careful deliberation. ‘Much of what my colleague said would have been perfectly true according to generally held medical and physiological knowledge – until recently.'

‘Which implies that you feel it is no longer correct?' prompted Prideaux.

‘There is very recent and still-ongoing research from several parts of the world which reveals a fundamental flaw in Dr Smythe's interpretation of his findings concerning potassium in the eye fluids, on which this case largely rests.'

Down in the well of the court, Angus's red face became even ruddier, but he had had his say for the moment.

‘As part of my review of the evidence, I discovered that several pathologists have independently done research in Germany, Denmark and the United States, which shows incontrovertibly that the potassium level in the eye fluid rises progressively after death – to a lesser extent than blood, but still unrelated to externally administered potassium.'

Nathan held up a sheaf of papers in his hand. ‘Are these copies of publication drafts and personal responses to your enquiries by those researchers?'

Richard nodded, lifting his own copies briefly from the shelf in front of him. ‘Yes, I contacted Professor Braun of Cologne, Dr Stoddart in Chicago and Dr Kaufmann in Minnesota. They all kindly sent me the results of their work.'

The judge made a gesture and an usher took the papers from Prideaux and handed them up to the bench.

‘I have a number of carbon copies of all this work, my lord. No doubt my learned friend and his expert would like to see them. I also have spare copies for the jury, if you feel they would derive sufficient understanding from what is undoubtedly a very technical subject.'

There was a delay while papers were being handed around the court. Angus Smythe was given a set as he squatted on his chair, and there was a long silence as everyone scanned the flimsy carbons. After about ten minutes, with the court beginning to get restive, Prideaux began speaking again.

‘Dr Pryor, could you just summarize, in a way comprehensible to us laymen, the import of this work? First, can you tell me why this research was done in various parts of the world? Surely there has not been a global epidemic of potassium homicides?'

Richard risked a grin, in spite of the fraught circumstances.

‘Not at all, sir! This was done for a totally different purpose. Estimating the time since death is a very important forensic problem, because of alibis and the like. Most methods are notoriously inaccurate, but these gentlemen discovered the fact that potassium in the eyeball fluid rises progressively after death. They have been trying to use this as a measure of time since death by making a graph of potassium level against the number of hours – or indeed days – that have elapsed since death.'

‘So what is the relevance to this case, doctor?'

‘The second post-mortem on Mrs Parker was not carried out by Dr Smythe until the third day after death. Though the results of the three researchers are not identical, it is patently obvious that the concentration of potassium found by Dr Smythe is well within the expected levels for that period of time, some seventy-eight hours. So the interpretation that this level must have been due to the injection of extraneous potassium is now quite unacceptable.'

Nathan Prideaux wanted to nail this idea down firmly in the minds of the jury, who by now were looking bemused at this sudden turn of events.

‘Dr Smythe claimed that the eye fluid is immune from the changes after death that make the blood levels of potassium useless. What do you say to that?'

‘I'm afraid it's just not true. This was assumed, but until now no one has actually investigated it. Admittedly, it is much slower than in the rest of the body, but this new research shows that potassium leaks out of the cells in the retina – the inner lining of the eye that allows vision – and this is why they hope it will provide a new method of determining the time of death.'

Richard Pryor, at Nathan's request, went on to quote facts and figures from the research papers to consolidate what he was claiming, while the judge, barristers and prosecution expert followed it on the documents they had been given. From the glazed look on the faces of some of the jury, it was obvious that they had no idea of what he was talking about, but soon Prideaux put them out of their misery by diverting on to a new tack.

‘Dr Pryor, I think you also have a second reason for disputing Dr Smythe's conclusions?'

‘Indeed, though I admit that I, too, was unaware of it until I began researching all aspects of potassium and eye fluid. Unlike the new discoveries in Germany and America, apparently this has been known to physiologists and biochemists for a long time. I'm afraid it's a problem with all sciences, that there is so much knowledge available, but it tends to be kept in separate boxes, until someone actively seeks it out.'

‘And what was in this particular box, doctor?'

‘Dr Smythe quite correctly said that death occurs very rapidly on injection of strong potassium chloride solution – which is the allegation in this case. The heart stops very quickly, perhaps not instantly, but within a few moments. That is why it is used by vets to dispatch animals.'

‘And what is the significance of that?' asked the QC.

‘When substances such as potassium are injected into the bloodstream, it takes up to three hours for the substance to reach its maximum concentration in the eye fluid. This “equilibration” as it is called, cannot proceed if the heart has stopped, as there is no circulation to drive the substance around the body to reach the eyeball. So if an injection of potassium is sufficient to cause rapid death, there is no way that this extraneous amount can get into the eye fluid! Any rise in potassium must therefore be due to post-mortem leakage from the cells in the retina.'

He lifted up another document from his collection. ‘Though I said this has been known for years, I sought advice from clinical biochemist Professor Lucius Zigmond of St George's Hospital in London, who is an expert in what are called “electrolytes” such as potassium. He has provided a statement in which this delay in equilibration is positively confirmed, and which is also contained in a number of standard textbooks.'