Basically I think if you are carrying a knife and something bad happens, you will be held at fault by the law and by a jury or judge. The fact that you had a knife looks bad for you right from the start.
In my city we just had a court case all over the TV news last week, a couple in a bar started arguing because another guy in the bar apparently knew his wife when she claimed she had never met him, they went outside and were arguing in the parking lot, the other guy came outside drunk and tried to pick a fight. The married guy claims it was self defense and the other guy "walked into my knife" anyway the guy is stabbed in the heart and dies. Eyewitness accounts don't clearly support which side was the aggressor, the knife wielder is sentenced for manslaughter by a jury.
I think carrying a knife for "self defense" is unwise and likely to get you in trouble. I think that any more mundane object could be adapted and used for self defense while still appearing innocuous, for example any large heavy long object made of metal, wood or hard plastic. These days I don't want someone else's blood on me if they could have HIV hepatitis or something else.
The real reason I want a knife close at hand at all times is because of all the super strength recycled plastic packaging on all new products, manufacturers have finally succeeded in rendering the evolution of the human hand obsolete. I can no longer open plastic packaging without aid of a knife or scissors.
In future generations all people will be required to buy mechanical hands with computer chips by Microsoft that require daily multiple re-booting and authentication and an upgraded operating system every 6 months, tied to a 2 year service contract with AT&T for usage minutes. I have seen the future, and it looks like "Edward Scissorhands."
:foot: