ESR forensic specialist Dr Sally Coulson, who examined the can following the incident, told the court this afternoon the can used by Zhernov had been modified after it had been purchased.
"The lid of the can has had two holes made in it. One hole is on the side, which allows this colourless spray nozzle to poke through the side of the lid and the other hole has been made in the top of the lid, and this allows the original spray nozzle of the can to be depressed or pushed down when the lid is still in place.''
Unlike the cans made available in stores or straight from the manufacturer, the one used by Zhernov had a small tube inserted into the nozzle, which could poke through the hole created on the lid's side. Because a hole had been made in the top of the lid, the substance could be sprayed - through a small tube - without ever removing the cap, Dr Coulson said.
Zhernov, who is due to give evidence once the defence case opens, will argue he sprayed Toko in self defence.
His lawyer, Michael Bott, questioned Ms Peiwharangi's memory of the incident during cross-examination today, saying his client had a very different account of the day.
Zhernov felt threatened and said he was trying to spray his own clothes with oven cleaner to scare the dog away.
He also had a walking stick, which he used to try to fend off the dogs. Zhernov also submits that Toko was biting his boot, forcing him to use the spray to scare it away.
Toko is a cross between a staffordshire bull terrier and a labrador, and was 11-years-old when the incident occurred.
The trial, before Judge Chris Tuohy, is due to finish tomorrow.