Muirhead rose and commenced his cross-examination of the pathologist. ‘Professor Walker, can we deal with your examination of Mr Boyle? His death was caused by two gunshot wounds?’

‘Yes.’

‘I think you suggested that the gunman approached the car from the rear and fired through the driver’s window?’

‘Yes, that is my view.’

‘Presumably the fact that the window was shot out would assist you in that regard?’

‘Clearly.’

‘Can you tell the jury anything about the range involved here?’

‘When a firearm is discharged, flame comes out of the end of the barrel along with a certain amount of unburnt propellant as well as the projectile. There was no sign of burning on the skin surface, nor was there any trace of unburnt propellant. This means that the person who discharged the firearm was two feet or more away from the victim.’

‘Inside the car there is blood and brain matter splattered on various surfaces?’

‘Yes.’

‘I take it that the spread and pattern are consistent with the gun being fired into the car?’

‘From my examination, yes. The forensic scientists and ballistics people would carry out a more detailed examination.’

‘Did you see any sign that blood had sprayed out of the car?’

‘I’m not sure what you mean.’

‘Was there any blood spotting on the outside of the driver’s door or wing mirror, for example?’

‘Not that I saw.’

‘Or on the outside edges of the driver’s door pillar?’

‘Not that I saw.’

‘Was there any blood on the road surface beside the car?’

‘Not that I saw.’

‘May the jury take it that there is no basis for concluding that any of the deceased’s blood would have landed on the gunman?’

‘Anything is possible.’

‘No doubt it is, but can you answer my question?’

‘I could not rule it out totally.’

‘Did you observe anything to show that blood or tissue had sprayed out of the car?’

‘As I said, I can’t rule it out.’

Muirhead allowed his irritation to show and snapped back. ‘I did not ask you what you could rule in or out. Now will you answer the question I did ask you?’

The professor bristled. He did not care to be treated in this abrupt manner. He was not any old witness. He was the Regius Professor of Forensic Medicine at Glasgow University, after all. His reply was clipped.

‘No, there was no such sign.’

‘Thank you. I’m very much obliged. As far as Clark is concerned, you are satisfied that he was dead when he was dumped in the bin?’

The now slightly sarcastic tone did not improve Walker’s humour. Being roughly treated by counsel was inconsistent with the good professor’s perception of his status and dignity and he allowed his irritation to show.

‘I thought I had made that abundantly clear.’

‘Indeed you did. But is it possible to determine how long he had been dead at that point?’