When does Brown conduct the background checks during the hiring process?

Reason for asking is in the application there was no option for "don't contact my current employer" as some applications have. I am still waiting for my app to go active. Just had a friend put in a recommendation and I'm planning to attend the FAPA in Oct.

Trying to figure out when and if I should have a talk with my current employer in case they get a call from Brown and are caught off guard. If they do this after giving out job offers post interview none of this matters.

Thanks ahead of time.