Tower controller reported aircraft under their control had to slam on the brakes to avoid contact wi...

Narrative:

While providing training on outbound ground; the following event happened:aircraft X was given taxi instructions to runway 28R/N5 intersection departure. The session was extremely heavy/mostly difficult for the cpcit career professional controller in training. After giving taxi instructions; the cpcit moved on to other tasks that needed to be handled. After the session; the flm told both the cpcit and me that aircraft X had to 'slam on the brakes' to avoid hitting another taxiing aircraft on an adjacent taxiway. When that happened; a flight attendant was injured; forcing the aircraft to return to the gate.after watching and listening to the replay; it is obvious that both the cpcit and I missed a traffic call that should have been made to avoid the situation.while I cannot speak for the cpcit; cpcit may have thought that the aircraft established on the a taxiway would be blocked by that heavy jet; allowing the time needed to taxi aircraft X off gate xwe. However; after viewing the replay; I do not believe this is the case. My focus was on things elsewhere on the airport when this aircraft was taxied; and I missed the instruction and traffic call.the only thing I can recommend that would have prevented this from happening is to ensure that my scan; as well as the cpcit's scan is complete and through; and that any coordination between outbound ground and inbound ground is accomplished.I will continue to work on my abilities as a veteran controller to maintain my scan; and pass those traits on to those who I train.

Original NASA ASRS Text

Title: Tower Controller reported aircraft under their control had to slam on the brakes to avoid contact with another taxing aircraft; resulting in a Flight Attendant injury.

Narrative: While providing training on outbound ground; the following event happened:Aircraft X was given taxi instructions to Runway 28R/N5 intersection departure. The session was extremely heavy/mostly difficult for the CPCIT Career Professional Controller In Training. After giving taxi instructions; the CPCIT moved on to other tasks that needed to be handled. After the session; the FLM told both the CPCIT and me that Aircraft X had to 'slam on the brakes' to avoid hitting another taxiing aircraft on an adjacent taxiway. When that happened; a flight attendant was injured; forcing the aircraft to return to the gate.After watching and listening to the replay; it is obvious that both the CPCIT and I missed a traffic call that should have been made to avoid the situation.While I cannot speak for the CPCIT; CPCIT may have thought that the aircraft established on the A taxiway would be blocked by that heavy jet; allowing the time needed to taxi Aircraft X off gate XWE. However; after viewing the replay; I do not believe this is the case. My focus was on things elsewhere on the airport when this aircraft was taxied; and I missed the instruction and traffic call.The only thing I can recommend that would have prevented this from happening is to ensure that my scan; as well as the CPCIT's scan is complete and through; and that any coordination between outbound ground and inbound ground is accomplished.I will continue to work on my abilities as a veteran Controller to maintain my scan; and pass those traits on to those who I train.

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	1711610
Time
Date	201912
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Route In Use	None
Flight Plan	IFR
Aircraft 2
Make Model Name	Widebody Low Wing 2 Turbojet Eng
Flight Phase	Parked
Person 1
Function	Instructor Local
Qualification	Air Traffic Control Fully Certified
Experience	Air Traffic Control Time Certified In Pos 1 (yrs) 15
Events
Anomaly	ATC Issue All Types Conflict Ground Conflict Critical Flight Deck / Cabin / Aircraft Event Illness

Tower controller reported aircraft under their control had to slam on the brakes to avoid contact with another taxing aircraft; resulting in a flight attendant injury.