With internet, self check in and the like, where else do you suggest before the bag gets on board?
We actually don't know if this passenger was hit by an overweight/oversize bag, and whether or not it belonged to the victim.
Given the specifics of this flight - at LHR T5 everbody's hand baggage should be screened for size before conformance (i.e. going airside) and again at the gate....if you have two item the smaller items get a natty little yellow tag meaning you should put it
under the seat in front....
As PC767 has said the backstop is the gate staff....
FWIW I have very recently seen a (BA) flight delayed to put hand baggage in the hold. If the commander doesn't sign the paperwork until handbaggage issues have been resolved it's kind of difficult for the ground staff to do a runner and pull the steps/jetty
