A ZDC Controller witnessed an airspace incursion. The skills check was being conducted in an adjacent sector.

Narrative

While providing OJTI on R 16; a limited data block was observed approximately five miles northeast of the Flat Rock VOR. It was traveling southwest bound and was level at FL280. The tag was brought up and it showed that a C551 was flying through our airspace without a point out or hand off. Sector 32 had track control of the aircraft. We quick looked the surrounding sectors and saw that there was no traffic for that aircraft. We had no traffic for the aircraft as there were only two other airplanes in our sector at the time and they were over forty miles away. We checked with the sectors around us and found that that aircraft was known traffic to them. We continued to watch the aircraft until it left our airspace since it was now known traffic to us. It was never in any conflict with our traffic. The aircraft traveled approximately 35 miles through the northwestern corner of our airspace. A skills check was in progress at the sector responsible for making the point out to us. The Supervisor doing the skills check was qualified to work that sector so a CPC was not plugged in and monitoring. I do not know if the skills check was a distraction to the operation but it may have been better to have a CPC monitoring the sector to allow the Supervisor to attend to the evaluation.