The Ti Lite requires manual assistance to open. Various dictionary sources have daggers as sharpened on both edges or not. I appreciate the notation that daggers are legal to own but not to carry, and add that I was thinking in terms of carry when I did the OP.
I found the best definitions of daggers in a couple of old Webster dictionaries dating back to a time when daggers were probably more common than today.
Webster 1828 http://1828.mshaffer.com/d/word/dagger" onclick="window.open(this.href);return false;
DAG'GER, n.:1. A short sword; a poniard.
Webster, 1913 http://machaut.uchicago.edu/cgi-bin/WEB ... ORD=dagger" onclick="window.open(this.href);return false;
Dag"ger: 1. A short weapon used for stabbing. This is the general term: cf. Poniard, Stiletto, Bowie knife, Dirk, Misericorde, Anlace
The common thread seems to be daggers a weapons designed primarily for stabbing and in general did have both edges sharpened, but not always. A knife designed for cutting might not classify as a dagger, regardless of it's stabbing capability which, of course, all knives are capable of to some degree by their very shape.