njungeb said:
To what extent do you have to participate?
As much or as little as you wish. Just don't lie. If you do not want to talk with them, say so. However, if you are later subpoeaned to court, you may be compelled to testify unless you invoke your 5th Amendment right to self incrimination ... but, what you have to say would have to tend to incriminate you in a criminal act - it's not an excuse to just keep your mouth shut.
Do you have to participate at all?
See above.
A friend is being investigated for something we truly have no knowledge of and we are not sure whether we would like to even talk with the detective or not. The incident happened before I had even met this friend.
Well, I can think of a few reasons why they might want to talk to you ... to verify some parts of the suspect's story, to clarify timelines or other issues that may have taken place afterwards, etc.
You can either decline, or, you can cooperate. if you suspect that this can in any way bite you in the buttox, then you might want to talk with an attorney.
- Carl