Canada's civil liberties watchdog is calling on investigators in the Sonia Varaschin murder investigation to "immediately stop" voluntary DNA sampling.

The Canadian Civil Liberties Association is calling the practice "coercive."

A civil liberties group is objecting to police plans to seek voluntary DNA samples in the Sonia Varaschin murder investigation. (Patrick Morrell/CBC)

Police said on Tuesday they are requesting individuals over the age of 18 to volunteer for DNA swabs that could be used in the high profile case.

Police claim they have DNA they believe could be linked to the killer.

"This practice, which does not involve prior authorization by a court, is highly coercive," the Canadian Civil Liberties Association said in a release Wednesday.

"Suggesting that such individuals can choose to provide DNA samples on a 'voluntary' basis is misleading, and ignores the coercive nature of police requests."

The group argued that DNA samples contain a wide range of information about a person's biological make-up and therefore, people should not hand those samples over to authorities without a court order.

Investigators, including the Orangeville Police Service and the Ontario Provincial Police, are expected to compile a list in the next few days, but the process is expected to continue for several weeks.

Police said there is no obligation to provide the sample and that participation is voluntary. The investigators also said that the samples would only be used to compare DNA recovered during the investigation, and that the samples as well as other documents would be destroyed if there was no match.

This kind of search for DNA has been used before when Holly Jones, a young Toronto girl, was murdered in 2003, and it led them to her killer.

"It is not appropriate for police to conduct criminal investigations by process of elimination," said CCLA general counsel Nathalie Des Rosiers.

"Canadians have a legal right to refuse when police ask for warrantless access to their most private personal information. This is a bedrock principle of our system of justice, and one that the OPP is subverting by effectively coercing innocent people to hand over DNA samples to police."

Varaschin, 42, went missing last August and her bloodstained white Toyota Corolla was found at Orangeville Town Hall the same day her disappearance was reported. A bloody crime scene was also found at her Orangeville townhouse complex.

Varaschin's remains were found by someone walking through the woods about 13 kilometres east of Orangeville eight days later.