So you make it clear up front that while they will not be asked about any criminial convictions, they will be asked after and will simply have wasted their time

So you make it clear up front that while they will not be asked about any criminial convictions, they will be asked after and will simply have wasted their time. Plus you usually don't have just one good candidate, you typically have a couple, different people might even prefer different candidates. If you really only have on qualified candidate, what will you do if they quit?