I just looked over the application instructions and the question is about previous
convictions, not arrests, unless the application has changed since the instructions were published.
Here is the link:
http://www.cbp.gov/linkhandler/cgov/...obal_entry.pdf
It says very clearly on page 39 that the question is about previous convictions; I see no question asking about arrests. Same for NEXUS.
That is my point about the problem with online applications. In the old paper world, you could attach an explanatory letter on a debatable call to avoid claims that you are being deceptive where an answer involves a judgment call.
When I looked at the Global Traveler manual, it said to include expunged and pardoned convictions. I would think the feds are not obligated to respect state pardons. They generally do, but there are certainly exceptions. When you apply for law licenses in most states, for example they examine pardoned offenses as well as regular ones. Canadian pardons are useless for gaining entry to the US. You still need to apply for a waiver. I'm not talking Nexus, I'm talking ordinary admission.