Former Balfour Beatty engineer Nick Jeffries believes the manslaughter case turned on the evidence of Network Rail head of track engineering David Ventry.
A letter sent by Ventry to Balfour Beatty in December 1999 formed a key part of the prosecution case. In it, Ventry was alleged to have set out guidance for dealing with gauge corner cracking (GCC), the phenomenon that caused the rail break resulting in the fatal derailment.
Ventry took the stand on 5 March, day 21 of the trial.
He was unequivocal: 'If the standards and guidance had been followed, in my opinion the Hatfield crash would not have occurred, ' he told the court.
But the defence maintained that the guidance was confusing and seven days into his stint on the stand, Ventry admitted that he intended to issue clearer instructions when GCC was better understood.
Ventry also accepted that language used in communications issued after the crash was simpler and easier to understand than that employed in the letter.
He said it would have been a 'great advantage' if those who read the letter understood complex ultrasonic procedures.
Jeffries' QC Jonathan Goldberg suggested there was no precedent for the letter's contents and that it caused confusion among its recipients.
Finally, on 15 March, day 29 of the trial, it emerged that the letter contained a major anomaly. It stated that action only needed to be taken before 80Mt of traffic passed over a site with visible GCC.
This would not have been until in 2003, two years after the crash.
Ventry said the guidance was based on experience of GCC from the West Coast Main Line.
But he added that it transpired during investigations following the crash that 'what was happening on the East Coast Main Line was more aggressive than on the west coast'. MH