"The minute I give an example, people will say there's an excuse I can use to get off."
He said some people already got creative writing in with explanations, some of which "don't bear any relation".
Revenue from cellphone fines has reached $2.5 million in the three years since it became illegal.
Griffiths said his only performance target was reducing the number of road deaths.
"I really don't give a toss about the number of tickets," he said.
"In fact I would love to see the number of tickets reduced because that would mean fewer people were offending. That, to me, is the success measure."
Since 2007, at least 28 people have died on the road in crashes linked to cellphone use, and the number of fines are increasing as police continue to crack down.
"We've still got people dying as a result of cellphone use. I want to see that turn around," said Griffiths. "I want to see my staff come back in and say, 'we didn't catch any because they are all doing the right thing'."
Meanwhile, after the second lowest annual road toll in 60 years, of 307 last year, Griffiths has set a target of reducing the road toll to no more than 200 in the coming years.
"I'd like to see the number coming down to 200 or less, and I think that's achievable. We've all got a part to play in that and the thing I'm wanting to stress is there's a big role for communities to play."
He said a key factor would be reducing the drink-drive limit from 80mg of alcohol per 100ml of blood to 50mg, as the Herald on Sunday has sought through its Two Drinks Max campaign.
"What I'm seeing is more public understanding and acceptance of the logic behind lowering of drink-drive levels," Griffiths said.
"Certainly countries that have lowered their drink-drive levels have seen reductions in their alcohol related deaths and serious injury crashes."
This week, a Herald-DigiPoll summer survey found 65 per cent support for cutting the limit to 50mg.
However, the Government said it wants more evidence before making a decision.
Numbers
• 29,745 caught on cellphones
• $2.5m revenue
• 112 excused