. >> after having applied ninhydrin to the seat belt and allowing it to dry completely, i reexaminede seat belt for the presence of fingerprints and found none. >> but the killer left behind one piece of evidence. a 9 millimeter bullet found on the floor of the victim's jeep. when investigators searched henry sullivan's apartment, they found a 9 millimeter pistol. >> investigators found that sullivan was in possession of two 9 millimeter pistols, and that matched with the murder weapon that investigators had been looking for. >> one was inoperable. the other 9 millimeter handgun was test-fired into a tank of water. that bullet was microscopically compared to the 9 millimeter slug found in the van dusens' jeep. analyst erica henderson carefully examined the distinctive marks called lands and grooves made when each bullet goes through the barrel of the gun. >> when you look down the barrel of a firearm, you will see the ridges and valleys. these ridges and valleys, once a bullet is fired, will be imported on the bullet. so the bullet will also have these ridges and valleys. >> the test