You're going to take time away from your actual escape to make yourself less incriminating in case you are caught? Should he have been grinding up IDs at the Greyhound bus terminal in New York? Right after the whole city heard about the shooting? Or should he have waited until after the FBI plastered the nation with his face?
> if you owned a pair of scissors or a lighter or something
Scissors won't take care of fingerprints, let alone DNA. As for the lighter, again, where do you propose he do this without attracting attention?
Actually, I could see him having thought this would be easy to do, maybe even packing a lighter and scissors, only to realise in execution that you can't start burning IDs on a bus without someone noticing.
You can just deface it in any way and throw it out the window on a highway or into any trash can and it will quite literally never be found.
No. But you don't know how far behind they are when you dispose of it. It only becomes random plastic after they've lost your trail.
> can just deface it in any way and throw it out the window on a highway or into any trash can
Sure. Or you can keep it until it can be safely disposed of. Which carries fewer risks? We don't even have to hypothesise, we know for a fact that the IDs on his person didn't cause him to get caught. We also know him not having the IDs on him wouldn't have caused him to be less caught.
Now I'm not a valedictorian, but I'd like to think I could achieve that.
He was presumably en route somewhere. Disposing of a fake ID such that forensics can’t get anything useful off it isn’t easily done on the run / incognito. (And if his inspiration is the Unabomber, he presumably had more targets.)