Crown prosecutor Joshua Shaw said the dogs were not killed in the most efficient way possible, and even if it had taken 40 seconds for them to lose consciousness "that's 40 seconds too long''.
He also pointed out the considerable distress the dogs must have been under from guns going off and from seeing their companions being slain.
"The way that the dogs were described screaming and crying could certainly fall under that description.''
Campbell previously told the court the dogs' owner, Rowan Hargreaves, had asked him to kill the dogs on his property - an old quarry near Wellsford - because they had got "out of hand''.
He said he took Mendoza along as "another set of eyes'' and Mendoza helped take 21 puppies out of a campervan so they could be shot.
He said they were greeted at the property by Mr Hargreaves, who shook his hand.
"I asked him: 'You know, you must have a couple of favourites'. He said: `No, just shoot them all'.''
This contradicts Mr Hargreaves' evidence that he thought of his dogs as his "friends and family'' and could not watch as the two men shot them, including 21 puppies.
He did not intervene in the shooting because he "knew they had guns and we didn't and I sure as hell didn't want to join my dogs''.
He agreed to some dogs being destroyed but not all of them.
Mr Hargreaves said in the days before the shooting he himself put down two of his dogs after he heard one mauled Mendoza's dog. He had also caught another dog in a neighbour's chicken coop.
Judge Mary Beth Sharp is expected to deliver her verdict tomorrow afternoon.
