This is the split-image view of a positive bullet match through a comparison microscope. The standard practice of the Dallas Crime Lab was to always place the evidence item on the left and the test-fired item on the right.

To most people, forensic bullet and cartridge-case matching means firing test shots from a suspect's gun and then using a special microscope to compare the markings to bullets or cases found in a victim or at a crime scene. The comparison microscope allows two bullets or cases to be mounted separately but viewed side by side through a split-image eyepiece. That makes up the bulk of the workload but wasn't always the most interesting of lab activities, at least not for me.

Interesting cases are challenging cases--ones where the investigating officers and lab people work closely to reconstruct a sequence of complex events that, hopefully, bring a suspect to trial. For me, the "no-gun cases" fell into the interesting category.

Connecting Random Cases
You don't need a multi-million dollar forensic facility to tell you cases are related if they happened over a few hours with a lot of witnesses. But what if the events are separated by weeks or months, cover several jurisdictions, and the only witnesses were murder victims? Good investigative methods, including centralized lab support, can tell detectives if events are related. If a firearm is used, the evidence it creates--fired bullets and cartridge cases--can help link events even before the firearm is recovered.

Because it persisted so long and affected several jurisdictions, a string of robbery-murders at little "mom and pop" grocery stores sticks in my mind. What we thought to be the first case had two dead victims and three .38 Special 158-grain lead RN bullets with Winchester's distinctive Lubaloy coating. The general pattern of rifling was clear--six lands and grooves with a left-hand twist. That made us about 99 percent certain that a Colt revolver had been used. This alone was unusual; as I wrote in a prior column, we found that criminals seldom showed good taste in firearms.

We could positively match two of the three bullets, showing they were from the same gun. The other had decent markings that suggested it was also from the same gun, but impact damage precluded our meeting the strict standards we imposed for labeling something a match.

Soon there were other robbery-murder cases in small grocery stores in the same area, and we ultimately had three more bullets just like the first. Again, damage prevented a conclusive match, but we could see enough to tell the officers that the cases were likely related.

The case broke when the bad guys used up their six Lubaloy loads and scored some M41 ball ammo in terrible shape. In yet another robbery, they aimed the gun at a storeowner's face and pulled the trigger; the cartridge failed to fire. The storeowner bolted down the canned food aisle, hurling cans of beans at the pursuing robber, who fired again. This time, the cartridge fired, but it was a squib. The low-velocity 130-grain FMJ bullet struck the clerk in the forehead and bounced off. It was enough to knock out the owner, but it saved his life.

The bad guys assumed the big red gash on his forehead was a lethal injury and resumed their ransacking of the checkout counter. When the clerk awoke, he had a whopping headache but a clear memory of what had happened. Using his description of the suspects' actions prior to the first attempt to shoot him ultimately broke open the case, but not before the deadly duo claimed more victims.