Tower controller trainee and trainer reported not noticing an aircraft taxiing across a runway while...

Narrative:

I was training with an instructor on local control. The event started with me verbally requesting the inactive runway 17; to which ground control gave me permission to use. The memory aid was used to indicate the runway was now local control jurisdiction. After which I moved my focus to the training C172's that were in the active runway 8's downwind. I gave the C172 holding instruction to protect for a possible go around on the crossing runway. As aircraft X became closer to runway 17 and was committed to the landing I returned my focus to the C172's in the downwind for runway 8. Instructed the C172's to roll out on the downwind to rejoin the pattern. During the roll out the second C172 holding east of the crossing runway rolled out before the first C172 west of the crossing runway. I decided to re-sequence and issued control instructions. One of the C172 misunderstood the instructions and began to converge with the other so my attention was out the window looking at the aircraft which put my back to aircraft X which was in the short final area. I resolved the situation with the C172's and returned to my scan to find aircraft X rolling out and aircraft Y had finished it's crossing of aircraft X's landing runway at taxiway D.I'm not sure of when aircraft Y began its crossing or if aircraft X noticed the incursion. Simultaneously as I noticed the incursion aircraft X was committed to landing and the nose of the aircraft was dropping and it would have been unsafe to send the aircraft around. At their closest they appeared 2000 plus feet away. No pilot in command acknowledged the incursion or question any instructions. The controller instructor was focused with me on the actions happening opposite of the runway incursion. All memory aids and communication were used according to standards. I have no knowledge of what could have happened or instructions given to aircraft Y on ground control. Due to my lack of knowledge on what happened in the ground control position I have no recommendations. All current procedures and memory aids were used appropriately.

Original NASA ASRS Text

Title: Tower Controller trainee and trainer reported not noticing an aircraft taxiing across a runway while another aircraft was landing due to distraction from traffic in the pattern.

Narrative: I was training with an instructor on Local Control. The event started with me verbally requesting the inactive Runway 17; to which Ground Control gave me permission to use. The memory aid was used to indicate the runway was now Local Control jurisdiction. After which I moved my focus to the training C172's that were in the active runway 8's downwind. I gave the C172 holding instruction to protect for a possible go around on the crossing runway. As Aircraft X became closer to Runway 17 and was committed to the landing I returned my focus to the C172's in the downwind for Runway 8. Instructed the C172's to roll out on the downwind to rejoin the pattern. During the roll out the second C172 holding east of the crossing runway rolled out before the first C172 west of the crossing runway. I decided to re-sequence and issued control instructions. One of the C172 misunderstood the instructions and began to converge with the other so my attention was out the window looking at the aircraft which put my back to Aircraft X which was in the short final area. I resolved the situation with the C172's and returned to my scan to find Aircraft X rolling out and Aircraft Y had finished it's crossing of Aircraft X's landing runway at taxiway D.I'm not sure of when Aircraft Y began its crossing or if Aircraft X noticed the incursion. Simultaneously as I noticed the incursion Aircraft X was committed to landing and the nose of the aircraft was dropping and it would have been unsafe to send the aircraft around. At their closest they appeared 2000 plus feet away. No pilot in command acknowledged the incursion or question any instructions. The Controller Instructor was focused with me on the actions happening opposite of the runway incursion. All memory aids and communication were used according to standards. I have no knowledge of what could have happened or instructions given to Aircraft Y on ground control. Due to my lack of knowledge on what happened in the Ground Control position I have no recommendations. All current procedures and memory aids were used appropriately.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1386318
Time
Date	201609
Local Time Of Day	0001-0600
Place
Locale Reference	PNS.Airport
State Reference	FL
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	Light Transport
Operating Under FAR Part	Part 91
Flight Phase	Landing
Route In Use	Visual Approach
Flight Plan	VFR
Aircraft 2
Make Model Name	Small Aircraft
Operating Under FAR Part	Part 91
Flight Phase	Taxi
Route In Use	None
Flight Plan	IFR
Person 1
Function	Local
Qualification	Air Traffic Control Developmental
Person 2
Function	Instructor Local
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 1
Events
Anomaly	ATC Issue All Types Conflict Ground Conflict Less Severe Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Ground Incursion Runway

Tower controller trainee and trainer reported not noticing an aircraft taxiing across a runway while another aircraft was landing due to distraction from traffic in the pattern.