Sal, sorry to hear that you are involved in a court case, and I hope everything works out for you.
I usually carry at least one standard sized SAK plus at least one one handed opener, which range in size from, say a Chinook II or Benchmade Blackwood if I am hiking, down to the Kiwi if I really don't want to seem threatening. ok, I ocnfess, I ALWAYS have the Kiwi. For an "average" size, I like the Persian. (Do we detct some prejudice here--ok, plead guilty). So anywhere between 2-4.5" would be the answer.
I have been carying knives since about second grade. When I was a kid in school, nobody cared-- everybody had a pocketknife (as we called them).
My knives are used for anything from opening packages, cutting 1/8" thick aluminum sheeting, making shelter, and damn near everything I can think of.
Cutting insulation off cables. Cutting tubing. Cutting cable ties. Preparing my lunch: slicing vegetables, fruit, etc. In my case, you might as well ask what I use my thumb for (and no smart remarks, guys).
Here is one example that may help. A group of people were opening a package (wood, cardboard, etc) with the only tools they had at hand which were single edged razor blades. One of them was (not too seriously) cut when the blade slipped out of his hand. I finished the job with whichever knife that I had on me at the time-- and needless to say, I have nver been injured using knives for this type of thing. And, I might add that any knife I carry is gonna be about as sharp as that single-edged razor blade.
Again--good luck and let us know if we can do anything to help.