Spearing is sorta like determining if a person is "public figure". The usual test is did the person hire a press agent of any kind. If you did, you're a public figure and a lot of your protections against being libeled don't apply.
The test for spearing is whether you wore a "horse collar", the now almost obsolete ring of foam (usually) that prevented your helmet from snapping back and your neck from bending too much. Forensic is right about the crown of the helmet rule, but the reason why even the "facemark in their numbers" version of spearing was banned is the very real risk of injury. When everybody on both sides of the ball was wearing a horse collar, it was obvious that the rash of neck injuries reported was real.
I wore4 a horse collar during most of my late high school and college career. And, yes, it was fun to hit people that way. Too dangerous, however.