''There's a lot of pain he's been going through,'' said the victim's son, Barry Homan.
Counsel Andrew More also stressed the ordeal his client had undergone, while acknowledging it was incomparable to the plight of the victim and her family.
''He has described these last few months as the hardest time of his life and it has had an obvious effect on him,'' he said.
''He lives by a mantra of 'do no harm to others'.''
More said the defendant had used yoga and meditation to cope with his guilt, which he felt particularly keenly because of his spiritual beliefs.
Trotter-Johnson was a vegetarian, he told the court, ''who says a prayer for the plants he eats before he eats them''.
Herbert had parked her car in Great King St on the day in question - she was off to get some seafood.
She returned to the intersection with St Andrews St five minutes later and waited for the green crossing light to illuminate.
Trotter-Johnson was waiting at the lights to turn right at the same time and three seconds later, when his light turned green, he set off.
''The victim was there to be seen and he did not see her,'' More said.
When the defendant hit Herbert, she was launched on to his bonnet and then thrown on to the road 10m further on when he stopped.
The victim suffered a serious head injury and a broken femur, and was on life-support before she died.
It was not the first time Trotter-Johnson had been responsible for an accident. Judge Flatley noted he had been convicted of careless driving causing injury in 2009.
''These intersections can be difficult, especially when motorists are given the green light at the same time as pedestrians,'' he acknowledged.
Homan also took a compassionate stance, saying: ''It's an accident. Those things happen.''
He said his mother would be remembered for the things she did for others.
''We are very sad,'' Homan said. ''Family, friends, the bowling club; they'll all miss her.''
Judge Flatley sentenced Trotter-Johnson to 150 hours community work and banned him from driving for nine months.
The defendant was ordered to pay $10,000, which he had borrowed from a friend in Australia, to Herbert's family.