Landing 25L at LAX, there is an expectation that you will be told to hold short of 25R at a particular intersection. Doesn't happen every time, but it happens often. Although the F/O read back the instruction correctly, expectation bias took over and they proceeded as though it was "hold short of 25R on Q".
Taxiing clear of the runway is a very busy time. Here's what the F/O was doing (737).
Clock, start (time engine cool down)
Transponder, from TA/RA to ON
Nav radios, deselect ILS frequency
Flaps, up
Stab Trim, set 5°
Autobrakes, Off
Flight directors, both off
Engine start switches, off
Exterior lights, set
Engine/wing anti-ice, off
Pitot heat, Auto
Trim Air, off
APU, start (or remember to start later, depending on the
It's a flow and it is always interrupted by radio calls, switching frequencies, and monitoring the taxi route and clearing for obstacles and traffic on the right side of the airplane. This creates a significant threat of error. This threat can be mitigated by careful attention to phraseology and the specified holding instructions. Additionally, VVM (Verbalize, Verify, Monitor) is used to ensure both pilots heard the same instructions, agree on what they mean, and that the Captain follows through in executing them.
There's a lot going on which presents threats for errors being made but the mitigating procedures broke down in this case. This is a good example of why the use, and understanding, of proper phraseology is important.