The pillow alleged to have been used as a murder weapon by Natalie Maher may not have been big enough to be effective, a defence counsel Evan Hughes told a Supreme Court jury.
Ms Maher, 48, has pleaded not guilty to the murder of her mother Veronica Corstorphine, 71, at Keane Street West, South Launceston on October 3, 2019.
Mr Hughes donned gloves to hold up the pillow, which he said more correctly would be called a cushion.
"Look at its size, really look at its size," he said.
"Think about the size of the human head and think about if this was applied to the face and the mouth."
Mr Hughes asked whether it was reasonably possible for a person wielding the object to be capable of stopping breathing for between one and 10 minutes as they struggle.
"This cushion is not a large object, we say that is not probable," he said.
He said a person under attack would turn their head to the side towards the air.
He said state forensic pathologist Donald Ritchey did not look at the pillow.
The jury has heard that Dr Ritchey's opinion was that the death of Ms Corstorphine involved another person after conducting an autopsy and viewing body-worn camera footage captured by police when Ms Corstorphine's body was found on October 29.
Mr Hughes said he had put it to Dr Ritchey that the pillow could have fallen onto the face of Ms Corstorphine.
"You might think when there were two other pillows on the head of the bed that the pillow could easily have come down in the course of a seizure," he said.
Dr Ritchey said he could not say it didn't happen.
He suggested that Ms Corstorphine could have died by suicide, by a natural cause or at the hands of an intruder.
Mr Hughes took the jury through Ms Corstorphine's bank records and cigarette purchases to demonstrate that she was a heavy smoker.
He said that it was reasonable or possible that Ms Corstorphine had a stroke as a result of smoking especially for a person prone to stress and with a history of stroke.
Justice Robert Pearce will sum up on Friday.
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