These are words Douglas Campbell, 20, used to describe his emotions after police knocked on the door of his Toronto apartment last week and asked him for a DNA sample.

Campbell's West End home is in the heart of the most intensive part of the police investigation into the slaying of 10-year-old Holly Jones, who disappeared on her way home from a friend's house early in the evening of May 12. Police canvassed the streets where Holly was last seen, asking men "over a certain age" and who met certain criteria for saliva swabs.

Investigators are not ruling out as possible subjects those who co-operate any more than they are ruling them in, Toronto police Sgt. Jim Muscat said at a news conference.

"They're all possible suspects, and it's all a matter of a process of elimination," he said.

Muscat said several people refused to provide samples. Campbell was one of them, saying he felt somewhat intimidated.

"I felt uncomfortable about it. . . . If I have doubts about it one way or another, I'm more likely to say no than I am to say yes. People knock on your door and ask for your DNA? . . . No, brother," Campbell said.

He said police were "OK" about his refusal. "But I felt really uncomfortable. I didn't trust them," he added.

Police have said samples will be used for the current investigation and then discarded. But Campbell wasn't so sure.

"I was kind of paranoid that, like, what if they did keep it on record? What if some scientists decided to keep the DNA and in 20 years used it for something?" he said.

Experts say such massive DNA sweeps can have a sobering social and legal price.

Besides challenging civil liberties and tearing neighborhoods apart, a sweep - known as a "blooding" - can compromise the value of any DNA evidence it yields.

"The police think they are being very clever, but proceeding this way could very well jeopardize their case down the road," said Sanjeev Anand, a law professor at the University of Alberta.

Individuals asked to volunteer DNA samples in a high-profile homicide case may feel they have no choice, setting up a later court challenge, he said.

"Make no mistake, it is a form of state-imposed coercion," Anand said. "Neighborhood pressure is a huge ingredient in whether someone actually exercises their constitutional rights.

"I think that person could make a very good case that their sample was obtained by coercion. It becomes a forcible seizure, and police have to establish it was reasonable. And they can't."

Alan Borovoy, director of the Canadian Civil Liberties Association, said a blooding is "an enormous intrusion into our personal privacy. No matter how it is dressed up, there is an element of coercion."

However, Borovoy said it is too early to judge whether the Toronto police have sufficient evidence to justify their sweep. What the case does emphasize, he said, is a need for a body empowered to review such tactics.

John Dixon, of the British Columbia Civil Liberties Association, said that as a prerequisite for obtaining a sample, police should have reasonable and probable grounds to believe an individual is a genuine suspect.

"If it were me, I would be a refusenik," he said. "The issue of principle is far more important than whatever transitory gain you may have from suspending civil liberties." Dixon also was skeptical about police assurances that DNA samples will be destroyed. He said it would be no surprise if they ended up in the national data bank.