‘Haven’t I read that this lividity becomes fixed after a certain number of hours, which can be used in timing?’
‘That is certainly in all the textbooks, but in practice it is very variable and often doesn’t occur at all,’ was the firm reply. ‘I’ve experimented myself and found it to be totally unreliable.’
Douglas Bailey was getting out of his depth here. ‘Can you explain that, Doctor Pryor?’
‘When the blood cells settle, they are still inside the veins under the skin, so that the dark reddish-purple colour is visible. The delay for this to happen is very variable — in fact, in some old or anaemic people, it is never visible. Now if the body is moved after death, such as being turned over, the blood may or may not reposition itself towards the new lowest areas. Sometimes it does, sometimes it doesn’t. For years, pathologists and police surgeons have tried to put a timeline on when it stops moving and becomes fixed. But even when fixation does occur, it’s so random in its timing as to be useless. I’ve copied out the opinions given for this and for timing rigor mortis from almost a dozen textbooks of forensic medicine and you will see that the range of disagreement runs to many hours, so it’s of virtually no value!’
He passed around a few carbon copies of Moira’s typing and waited until the three lawyers had scanned them.
‘So what about rigor mortis? That’s always held up in detective novels to be the bee’s knees for timing death,’ said Paul Marchmont.
‘Much the same criticism as with hypostasis,’ replied Richard. ‘There are generalizations, which are not at all accurate — and so many exceptions to the generalizations that no useful rules remain.’
‘Can you expand on that a little, doctor? asked Penelope Forbes. Angela watched her partner and recognized him getting into lecture mode. She knew he was good at it and wondered if his students in Bristol University appreciated him.
‘Rigor is stiffening of all the muscles of the body after death, due to a chemical reaction affecting their proteins. The problem is that there are a number of factors which affect the speed and intensity of this stiffening. For example, strenuous activity shortly before death hastens it appreciably, which is why battle casualties often have a rapid onset of rigor. The same happens after electric shock. Then temperature also accelerates it and cold delays it. I’ve seen a body dead in the snow for some days with no rigor, but as soon as it was brought into the mortuary, it stiffened up.’
‘It was a very hot period when Arthur Shaw died in June last year,’ interjected the solicitor. ‘It was virtually a heatwave.’
‘I realized that, Mr Bailey, which was why I phoned the weather people at Bristol Airport the other day. Their records showed that the temperature, even at midnight, was much higher than usual for that date, so there’s another factor to use in the argument.’
‘What effect would that have had?’ asked the QC.
‘Rigor could have come on faster, giving the impression that death had occurred earlier than it really did. The trouble with that argument is that the accuracy of back-calculating is so poor that trying to adjust for temperature is not much use.’
‘So the old formulae given in the books I’ve seen for calculating from rigor is just not correct?’ persisted Miss Forbes.
Richard shook his head. ‘It’s the old story of the bell-shaped curve, which pervades much of biology. There’s a high point on the graph where most of the cases lie where, say, rigor comes on in three to six hours or so. But on each side of the peak, there’s a slope where the other cases lie, either earlier or later. If the bell is high and narrow, then accuracy is better, but if, as with rigor, the bell is low and flat, then there’s no chance of accuracy.’
He cleared his throat. ‘And that’s just for the onset of rigor. It increases in strength, then eventually passes off, called resolution, but the time when that happens is even more unpredictable. Unfortunately, many of the textbooks stick to the myth of a reliable timescale and copy it from edition to edition, because there’s nothing better to replace it with.’
‘You sound a bit of cynic, doctor,’ observed Paul Marchmont with a smile.
‘I prefer to think of myself as a realist,’ replied Richard. ‘The younger generation of pathologists are hopefully more critical of these sacred ideas of the older, dogmatic school. I met a German pathologist at a meeting last year, who is combing all the medical literature for over a century to list the variations in opinions about hypostasis and rigor.’
‘We’ve got stomach contents next; are you just as pessimistic about those?’ asked the senior barrister.
Richard rolled his eyes towards the ceiling. ‘Even worse! The old legend about stomach contents emptying in about two and half hours is again the top of the biological bell, but there are even more variable factors. The type of food, amount of liquid in it, amount of starch, personal variation and even variations in the same person. You can measure the speed of emptying in Bill Smith one day, then give him the same food another day and get a different answer! Fear, injury, coma, pain and emotional upset all modify the speed of digestion and emptying. To use it to calculate a time of death to within an hour is frankly ridiculous!’
‘Is examining the stomach contents of no use whatsoever, then?’ asked Douglas Bailey.
‘Only in the very broadest terms, insufficient to use as probative evidence. It might tell you what the last meal was and therefore you’d know that death occurred after the time it was eaten. For instance, if a man ate a curry one evening and was found dead two days later with a stomach full of curry, you’d know he hadn’t lived long enough to have his usual ham and eggs for breakfast next day.’
Angela came back here, as this was partly her province.
‘Even that’s not easy, unless digestion had not proceeded very far. We can often identify certain foods under the microscope, like meat fibres and some vegetables — but we’re not like the sleuths in crime novels, who can discover that the deceased had consumed a salmon sandwich and a cup of Earl Grey tea three hours before death!’
Marchmont held up his hands in mock surrender. ‘I get the point. Now what about temperature, which you said was the best method?’
‘Well, I said the least inaccurate,’ amended Richard. ‘Doctors have been trying since about 1840 to devise a formula to calculate time of death from the obvious drop in temperature after death — unless, of course, you happen to die in some parts of the tropics, where the post-mortem temperature actually increases!’
‘I don’t think Bristol comes into that category,’ said Douglas Bailey wryly.
‘No, but the temperature at the scene is very important, and we know that Shaw was killed during a Bristol heatwave,’ countered the pathologist. ‘The problem is that the investigation was poorly carried out, as no one took the room temperature nor the body temperature when the scene was visited. Doctor Mackintyre didn’t attend the scene and didn’t even see the body until the afternoon, over six hours after it was found, when he eventually put a thermometer in the rectum.’
‘And that matters in calculating the interval?’ asked Marchmont.
‘It’s vital, as for at least six hours, the body was cooling in the mortuary, no doubt much colder than the flat in St Paul’s, which distorts the cooling curve. We should really find out whether the place was air-conditioned, as some big city mortuaries are, which would increase the cooling even more. I’ve actually heard of a case where the body was put in the refrigerator for some hours until the post-mortem and then the pathologist took a temperature!’
‘So you can castigate any attempt at arriving at an accurate result?’ asked Penelope.
‘Certainly, I can! Even when the best procedures have been followed, the accuracy is poor and cannot be narrowed down to less than a couple of hours either side of the calculated time. It’s traditional to use a rule of thumb that a body cools at about one and half degrees Fahrenheit per hour, but all one can say about that is that if the answer turns out to be correct, it must be sheer luck!’