He used a backpack as a shield and started filming up her skirt. He captured images of her upper thigh area but a shopper caught him in the act.
When approached by police, Rushton admitted that his actions weren't impulsive, and he spoke of his sexual sickness.
Judge Nick Webby described the act at today's sentencing as a gross breach of the victim's personal privacy.
"She was vulnerable and should have been able to go to the mall without being photographed."
He faced a maximum penalty of 18 months imprisonment.
Rushton's lawyer Bruce Hall asked for a 25 per cent discount for his guilty plea and mentioned this was his first sexual offence charge in his criminal history.
"The most important thing is for Rushton to get the help he needs."
Rushton was sentenced to four months of community detention and 12 months of intensive supervision.
