Chris, I am not familiar with the Ohio case law, but I would assume that any reasonably competent prosecutor can establish that just about any knife is a deadly weapon under both parts of the definition.
Ohio law is a mess on the knife as a deadly weapon thing. City of Columbus v. Dawson (1986), 28 Ohio App.3d 45 held that a knife is not presumed by law to be a deadly weapon. To prevail on a CCW charge involving a knife, or something like the case in the OP, the State must prove beyond a reasonable doubt, either: “1) that the knife was designed or specifically adapted for use as a weapon or 2) that the defendant possessed, carried, or used the knife as a weapon.” State v. Cathel (1998),127 Ohio App.3d 408, 412.
Sounds good so far, but then it gets kind of murky. A judge in Pickaway County was quoted saying "The record is devoid of any evidence which demonstrates beyond a reasonable doubt that this knife was designed or adapted for use as a weapon. It was neither a switch or other spring-loaded blade, nor a gravity blade capable of instant one-handed operation, and differs only in its somewhat greater length from the familiar type of clasp knife carried as a useful tool by thousands." State v. Ratcliff (Oct. 26, 1983), Pickaway App. No. 82 CA 13. This sounds good, unless you are carrying a Spyderco, or an assisted opening knife. It worries me a bit.
IMHO, the best bet would be for counsel to argue that the knife was with rescue/medic gear, but at the same time file a motion in limine to exclude the two airsoft guns also found in the car, as well as the stun gun found in the car. The prosecutor might try to get all of that in as circumstantial evidence that the boy was carrying "weapons."
