8.2.2.4 Internal Audit Plans -
"Internal audits shall cover all quality management related processes, activities and shifts, and shall be scheduled to an annual plan."
When you set up your annual audit schedule you could include the off-shifts in the scheduling, or simply record the shift overlap on the audit report. There is no set rule on how you have to do this. QS-9000 required off-shift as well and I used a separate checklist for them. There is usually a lot less happening on the off-shifts here and not as much to review. The key is you should have something to show you include the off-shifts (schedules, audit reports, notations on the day shift audits etc.).
Dave