"The idea of aiming for a leg is just television stuff.
"This idea that you can be a sharpshooter when things are happening in split seconds, just isn't reality."
Cahill said the inquiry would uncover the full facts, but on the information currently public, a Taser wouldn't have been appropriate.
"Tasers often fail to deploy appropriately. They're much less accurate, so you can miss completely.
"Or they can deploy and land in heavy clothing, and not act.
"You don't have the option of a second chance when someone's swinging a machete at your head."
Cahill said the incident was part of a problem of rising violence being encountered by police.
Police Association statistics show that serious assaults against police have risen 20 per cent.
"Obviously, when there's an increase in those assaults, there will likewise be an increase in response that's required to defend officers.
"We've been saying for a while that we need to do something about the assaults on police.
"It starts with minor stuff. If that isn't dealt with appropriately by the courts, then that's seeing as police as fair game, you can have a crack at them.
"That leads to the more serious assaults."
The officer involved is now on leave.
A police representative told the Herald the name of the 44-year-old man who died may be released later today.
