Not a lawyer, but Canada's system differs in a few ways from the US. There's no right to have a lawyer present, only to speak to a lawyer (usually by phone). So

Not a lawyer, but Canada's system differs in a few ways from the US. There's no right to have a lawyer present, only to speak to a lawyer (usually by phone). So you're on your own in the interrogation room. If you're not being charged with anything, you're not required to voluntarily show up for an interrogation. If you're detained, you can always ask "Am I free to leave?" and, if they answer yes, just walk out. Police are permitted to keep asking you the same question even if you repeatedly say "My lawyer has instructed me not to answer questions", but obviously there's a line where it will start to look abusive on the tape and where the interrogator will just get frustrated and end the interview. You can't be compelled to testify against yourself, but others can potentially be compelled to testify against you (on the condition that their testimony can't be used to incriminate them in the future).