Police decided on the mass screening programme, the first of its kind in Australia, after all leads failed in the hunt for a man who attacked and sexually assaulted the woman as she slept in the early hours of 1 January last year.
Teams of police in Wee Waa, in New South Wales, began knocking on the door of every household in town, 500km (310 miles) north of Sydney, early in the morning on Saturday.
Police decided on the mass screening programme, the first of its kind in Australia, after all leads failed in the hunt for a man who attacked and sexually assaulted the woman as she slept in the early hours of 1 January last year.
Civil liberties groups complained that the tests might be used for purposes other than the current investigation and that the police might infer that those who refused the test were guilty.
Fear in the community
The woman received serious head injuries in the attack and continues to suffer deep emotional trauma.
Police tested more than 200 of Wee Waa's 600 men on Saturday, and will continue the process on Sunday.
"It's no big deal, just a quick scrape inside your cheeks, it's pain-free," said 52-year-old farmer Frank Williams.
"Most of the community here are very happy to assist police. I mean really, we're talking about the sexual assault of a 91-year-old woman," Mr Williams said.
Presumption of guilt
However, some in the town complained that the whole programme was a futile exercise as the rapist was a seasonal worker and not a local man.
Michael Antrum, chairman of the regional Law Society's human rights committee, said the screening offered "a frightening glimpse of a future police state."
Wee Waa's solicitor, David Sweeney, said he would not undergo a test and knew of five other men opposed to the idea.
"There really is a presumption that anyone who happens to be living in the area of Wee Waa this weekend is a suspect and is presumed guilty until proven innocent," Mr Sweeney said.
"They have to establish their innocence by submitting to this test that is contrary to the principles that protect civil liberties that have evolved over more than 100 years in the common law system," he added.
As well as undergoing saliva tests Wee Waa's men were photographed and their fingerprints taken and put into a central police data base. Police said that the samples and data would be destroyed once a man has been eliminated as a suspect.