People can choose to be good citizens and allow police into their homes in the search for missing teen Mariam Makhniashvili, but they also have the right not to, says the general counsel of the Canadian Civil Liberties Association.

But Natalie Des Rosiers told ctvtoronto.ca on Tuesday that the police do not have the right to be intimidating in the process.

On Monday, the Toronto Police announced an "unprecedented" door-to-door search effort to find the 18-year-old, who hasn't been seen since Sept. 14.

"You will expect a knock at your door and police will keep knocking on your door until they can identify that you are there," Det. Sgt. Dan Nealon said.

"We're also going to be asking to be invited inside your home to take a quick peek inside to ensure that there is no evidence in relation to this case with respect to you."

A reporter asked Nealon about the consequences of not co-operating.

"Certainly it makes our job a lot easier and takes our focus off of your door once you've answered our questions, (you've been) co-operative and then we can all move forward again. Certainly you have the right not to allow the police into your apartment or your place. We'll just have to move on and we'll work it out."

The police plan to knock on the doors of about 6,000 people over the next two to three weeks. There will be 60 plainclothes officers working 12 hours per day, seven days per week.

Des Rosiers said not inviting police in to search one's home is not sufficient grounds for the police to obtain a search warrant.

Under the Canadian Charter of Rights and Freedoms, section 8 states that "Everyone has the right to be secure against unreasonable search and seizure."

To conduct a search of a home, police need a warrant. Several Criminal Code sections lay out the law for officers to obtain warrants, she said.

"If a police officer wants a warrant to force himself or herself into a house will need to have reasonable grounds to believe that there is evidence relating the commission of a crime that is in that residence," Des Rosiers said.

"It's not going to be enough to say, 'Well, we're searching 6,000 residences in an area, and that person refused to co-operate,'" she said. "That's not going to be sufficient to amount to a reasonable belief that there's evidence in the home."

Des Rosiers said in TV crime shows, police sometimes threaten a person that if they don't co-operate, they will come back with a search warrant.

"It has to be an individualized search warrant. You can't have a generalized search warrant for a random look at 6,000 homes," she said.

Des Rosiers said if police come at an inconvenient time, and you don't want to help them at that moment, you have that right.

If they threaten to immediately get a search warrant, "that's intimidation and an incorrect statement about the law," she said.

"But we certainly want to encourage people to co-operate with police as much as they want. It's a good cause," Des Rosiers said.

Nealon said Monday that Mariam's disappearance is a "unique and difficult case."

Police still don't know if she is a victim of foul play, vanished on her own accord or whether something else happened.

The girl, who turned 18 in late October, after walking to Forest Hill Collegiate -- a high school in the Bathurst Street and Eglinton Avenue area --with her brother. When they arrived, she told her brother she would be going into the school from a separate entrance. But Mariam never made it to class and hasn't been seen since.

Last week, Ontario Provincial Police helped with the search by deploying their helicopter over the grounds of several parks and ravines. Police say nothing of interest was found in the search.

Last month police also seized dozens of computers from several public libraries in the area that were believed to have been used by the girl in the days before she went missing.

The only solid clue investigators have so far is the girl's school bag, which was found about a month after Mariam went missing. It was found in an alleyway behind a building on Eglinton Avenue near Yonge Street, a few kilometres east from where she was last seen.

To help jog people's memories, police have released an image of Mariam with the clothes she was wearing on Sept. 14 digitally added.