Usually in situations like that we prefer to do the criminal first, so that people can be interviewed, know what's at risk, and have their story told. The other way, people are a little awkward about giving up information, feeling that they may be held responsible in another way. But there is no reason they can't both be done conjointly. From a Criminal Code perspective, in our own code of conduct we often do those two things in parallel.
On April 25th, 2007. See this statement in context.