[logfromblammo]

Never say a number. If you want to give the option to the cop to give you a ticket with a lower fine attached, just say "my speedometer said I was okay." And that will probably result in a citation for an equipment violation instead of for speeding.

You can't say "I don't know," either, because that sets you up for some variation on negligent driving.

The safest response for the court record is "I don't answer questions without legal counsel present," but that is likely to provoke the cop into ensuring that there will be a court record.