He does so by checking the wood fragment in a microscope and finding out it was maple. Horatio then asks Speedle how much of the crime scene he remembers, and Speedle grumbles, "About three pages' worth. I put it in my F.I. report." "F.I."? "Fire Inspection"? "Finicky Individual"? "F***ing Inconsistent"? Horatio asks if Speedle remembers a pool table; he does not. Well, Horatio thinks the murder weapon was a pool cue, saying, "Pool cues are pressed wood -- twenty laminates per inch." That's a pretty highly-laminated piece of wood; too bad we have no idea why pool cues are laminated thusly. I'd tell you, but I'd rather take this time to go off into a tirade about the laziness of shows that toss around facts without context. I'm not just referring to this one, although it is a prime offender -- I take umbrage at any show where the writer gets lazy and decides they'll show how smart someone is by having them recall some esoteric tidbit, but they don't bother to demonstrate that said "smart" character is capable of processing information beyond its memorization and recitation. Any jackball can parrot facts and memorize trivia, but actual intelligence requires that one be able to consider facts within a larger context, and to synthesize both facts and context to come to a wholly comprehensive conclusion. It would have been so easy for this pool-cue scene to have gone down thusly:

Horatio: That's a pool cue, isn't it?
Speedle: How can you tell that from any other piece of wood?
Horatio: If you look at the grain, you'll see that it's pressed in long bars held together -- I'm going to guess that's laminate.
Speedle: Yeah? Ikea's furniture is laminated too.
Horatio: Not like this, Speed. Pool cues rely on layer upon layer of lamination to ensure a smooth surface. This way, there's no chance of a warped or bumpy cue affecting the trajectory of the ball.
Speedle: Physics counts for everything in that game.